A second round of Iraqi Scud missiles hit in and around Tel Aviv shortly after dawn today, raising the odds that Israel would retaliate, thus widening the Persian Gulf War and threatening the stability of the U.S.-led coalition arrayed against Iraq.

The attacks occurred around 7:20 a.m. local time (12:20 a.m. EST) and followed by one day an initial wave of Scud missiles fired against Israel.

The Israeli government ordered citizens to don gas masks, although reports citing military authorities indicated the warheads carried conventional explosives rather than chemical weapons.

Israeli Health Minister Ehud Olmert said, "We have some casualties," and Tel Aviv Mayor Shlomo Lahat said three people were slightly injured. Civil defense officials put the number of injured at at least 10.

Asked about possible retaliation, Olmert said, "We will have to do something . . . . Unfortunately, the Americans couldn't stop it, so we will have to stop it." But he declined to elaborate.

The attacks came about 12 hours after President Bush had pledged "the darnedest search and destroy mission that's ever been undertaken" against Iraq's remaining Scud missiles, as U.S. officials carried out an intensive diplomatic and military program designed to keep Israel out of the conflict.

Bush, who had gone to Camp David for the weekend yesterday afternoon, was awakened shortly after this morning's attack and given a preliminary report on the explosions by national security adviser Brent Scrowcroft.

Allied bombers had combed western Iraq yesterday in search of the Scuds. U.S. aircraft reportedly destroyed at least six more Scud launchers. The United States also offered to rush additional Patriot missile batteries to Israel to help protect its cities from the kinds of attack that had struck Haifa and Tel Aviv early yesterday, bringing Israel to the brink of a decision to enter the war.

The swift retaliation by allied aircraft to the first round of attacks a day ago, coupled with intensive U.S. diplomatic efforts that included phone calls from Bush and Secretary of State James A. Baker III to Israeli Prime Minister Yitzhak Shamir, apparently had persuaded Israel to refrain from immediately striking back at Iraq. Air raid sirens three times sent thousands of Israelis to shelters in false alarms again last night before this morning's attacks.

Israeli anxiety after the first attack was mirrored in Washington, where U.S. officials said that the urgent calls to Israeli officials had produced no firm commitment by the Israelis on what they would do in terms of retaliation. One official said there had been "constant contact" with the Israelis yesterday to prevent the war from mushrooming into an even larger regional conflict that could shatter the allied coalition in Operation Desert Storm.

In his appearance in the White House briefing room yesterday afternoon, Bush urged the American people to resist the euphoria spawned by the first successful hours of the war. "We must be realistic," he said at a White House news conference. "There will be losses. There will be obstacles along the way. And war is never cheap or easy."

Senior military commanders echoed the president's caution, stressing the war had only just begun. "That large army is still sitting there and it has to be rooted out," Lt. Gen. Thomas Kelly, senior operations officer for the Joint Chiefs of Staff, told reporters yesterday.

Allied aircraft losses as of last night totaled eight, including four U.S. planes with seven crew members listed as missing. Intense search and rescue operations are underway, said Pentagon spokesman Pete Williams.

Pledging that the United States and its allies would prevail in their objective of driving Saddam's forces from Kuwait, Bush said: "I can guarantee the world that as every hour goes by, he is going to be less able to respond, less able to stand up against the entire world."

Bush's optimism evidently was shared by world markets. The price of oil continued to tumble yesterday, falling more than $2, closing at $19.25 a barrel on the New York Mercantile Exchange. That price was the lowest since last July. Oil companies continued to cut the wholesale price of gasoline, which eventually should be reflected at the pump. It was unclear what effect the latest attack would have when markets reopen after the weekend.

Televised images of the bombing brought modern weapons technology into American living rooms yesterday as millions of viewers watched a remarkable video sequence of U.S. laser-guided bombs destroying Iraqi runways, air defense buildings and an air force headquarters in Baghdad. Other footage showed the launching of a Tomahawk cruise missile, and a U.S. Patriot missile streaking from its canister in Dhahran and destroying an incoming Scud with a blinding flash and a boom.

But detailed assessments of bomb damage and the performance of U.S. weaponry remained skimpy. Whether the video successes released by the Pentagon were representative or anomalous still is uncertain.

Although the second day of the Persian Gulf War included hundreds of sorties against Iraqi air defenses and other targets, the centerpiece of the allied effort -- in urgency if not in actual number of bombing missions -- was the effort to destroy the Scuds.

U.S. officials believe that Iraq possesses about 30 mobile Scud launchers, but the number of reloads -- extra missiles -- is uncertain. U.S. intelligence estimates put the Iraqi Scud stockpile at 300 to 1,000. "They've been squirreling them away for years," one senior offical said. The allied bombers are searching for the Scuds with satellite imagery and special reconnaissance aircraft capable of detecting heat-emanating weapons.

"Finding the fixed launchers is a relatively easy business, but finding the mobile launchers is like finding a needle in a haystack," said Gen. H. Norman Schwarzkopf, commander of the allied force in Operation Desert Storm, briefing reporters in Saudi Arabia yesterday.

Allied bombers yesterday morning found and destroyed six of the mobile launchers with Scud missiles aboard aimed at Saudi Arabia; five other launchers had been located and were being attacked "relentlessly," Schwarzkopf said.

The allied air war has reached the planned plateau of about 2,000 sorties a day, Schwarzkopf said; congressional sources said 5 million pounds of bombs were dropped in the first 24 hours of the war, a daily ordnance load roughly comparable to that of the intensive Christmas 1972 bombing campaign in Vietnam.

U.S. commanders had expected additional Scud attacks on Israel and Saudi Arabia, as well as Iraqi attacks against U.S. Navy ships, possibly using Exocet missiles fired from helicopters, the Pentagon told congressional officials. U.S. forces in the gulf war now exceed 450,000 men and women.

The new Patriot missiles ordered to Israel yesterday will supplement two batteries already sent to the Jewish state earlier this month. Bush agreed to provide Israel with those missiles last fall under emergency military assistance laws, specifically citing the "increased threat from ballistic missiles in the Iraqi inventory."

But those batteries are not yet operational, Pentagon officials said, citing delays in shipment and in training air defense officers in the operation, maintenance and tactics of the complex system. Other experts suggested that the delays also reflected friction between the United States and Israel over how much control Americans would retain over the weapons.

Designed as an antiaircraft missile, the Patriots sent to Israel were already modified to serve as anti-missile interceptors, officials said. A Patriot shot down an incoming Scud over the Saudi Arabian city of Dhahran early yesterday morning.

Two of the false alarms that triggered the air raid sirens in Israel yesterday were based on warnings from U.S. intelligence, a senior Pentagon official said. American reconnaisance detected signs of an attack on Israel, although no Scud was actually launched. An Israeli military spokesman said the second alarm was triggered by a suspicious object which turned out to be a piece of a disintegrating Soviet satellite rocket booster. A third alarm sounded only in Jerusalem after an explosion of undetermined cause in the city.

U.S. warplanes began flying attack missions from Turkey yesterday following a vote by the Turkish parliament to permit offensive operations during Operation Desert Storm. Those planes, according to one official, were likely being used in the hunt for the Scuds.

Eleven Iraqi planes -- out of an air fleet of roughly 700 -- have been confirmed as shot down or destroyed on the ground, although others are believed to lie beneath the rubble of demolished hangars and shelters, Pentagon sources said. U.S. B-52s continued to strike troop formations and other targets, although only 10 to 20 tank kills -- of more than 4,000 tanks in Kuwait and southern Iraq -- have been confirmed, the congressional sources added.

Kelly told reporters that U.S. weaponry has "performed stunningly well" and that "we think we're doing pretty well" in following the allied battle plan. Iraq claimed to have several allied pilots in custody, but Kelly said he could not confirm that.

A key unknown, military sources said, is whether the intensive bombing will demolish Iraqi morale enough to undermine the army's fighting ability in a subsequent ground war. Allied forces are trying to cut water pipelines to some Iraqi troops, one source said, because "water's their big vulnerability."

The Navy also disabled or sank three Iraqi patrol boats, including a 147-foot missile boat with a crew of 35, Pentagon sources said. In the first two days of the war, U.S. Navy ships fired 196 Tomahawk cruise missiles, which cost about $1.3 million apiece. Most were targeted at reinforced targets. Iraqi nuclear facilities have been struck to the point that "we have impaired them to the point of non-existence," said Sen. David L. Boren (D-Okla), a member of the Senate Intelligence Committee.

The B-52s, escorted by F-15 fighters and Marine F/A-18 bombers, again attacked eight divisions of elite Republican Guards in northern Kuwait and southern Iraq yesterday, Pentagon officials said. The bombers attacked corps and division headquarters, while A-10 attack planes hit Guard tanks.

More than 500 sorties have been flown against the Guards, reflecting the U.S. conviction that units -- totaling about 150,000 soldiers -- are a critical "center of gravity" in breaking the back of Saddam's military.

Schwarzkopf and Bush both took pains to reiterate that Saddam personally has not been targeted except as part of a general effort to destroy the Iraqi command and control structure -- an effort which has included intensive bombing of the presidential palace in Baghdad and other sites Saddam is known to frequent.

Pentagon officials said that by not publicly targeting Saddam, they hope to preclude the ridicule that befell the military after Gen. Manuel Noriega managed to elude capture for a time after the otherwise successful invasion of Panama; in effect, Saddam is a prime target but U.S. officials believe that chances of killing him are marginal at best.

"We believe {Saddam} still is maintaining control over all elements of his armed forces," Rear Adm. John M. McConnell, the senior intelligence officer for the Joint Chiefs of Staff, said yesterday.

Bush signed an executive order yesterday afternoon allowing the Pentagon to keep military reservists on active duty for more than 180 days and call up to 1 million reservists to active duty. The Pentagon had requested the order because some reserve units activated at the beginning of the crisis in August were nearing their 180-day limit. Defense Secretary Richard B. Cheney said last week that he had no plans to use the authority to significantly increase the number of reservists called to active service.

Cheney also declared an "airlift emergency" yesterday and ordered 20 commercial airlines to provide as many as 181 aircraft to help ferry U.S. war supplies and equipment to the Middle East. The action put into effect the second stage of a long-standing agreement between the government and the airline industry to permit the commandeering of commercial jets in a crisis.

Earlier yesterday, Bush said he had "thoroughly discussed" developments in the gulf yesterday morning with Soviet President Mikhail Gorbachev. The call from Gorbachev came after the Soviets had condemned the Iraqi attack on Israel, an unusual turn for a country which once was Iraq's patron and Israel's enemy.

U.S. officials repeatedly have stressed their efforts to avoid killing civilians in the bombing raids, a policy which Pentagon sources said reflects both the political need to minimize non-battle casualties and a belief that Iraq will crumble faster if only military and industrial targets are hit.

Iraq reported 23 civilians killed in the first wave of attacks Thursday but has not released any casualty figures since. Baghdad Radio yesterday warned that "the war has just started . . . a war between good and evil." Iraqi Information Minister Latif Jassim told the Iraqi News Agency, "Not a few drops of blood, but rivers of blood will be shed." Iraq also claimed to have downed 94 allied planes, a figure disputed by U.S. commanders.

More than a dozen journalists who fled Baghdad and arrived in Jordan yesterday reported that Saddam's palace had been destroyed in a cruise missile attack and that the defense ministry also was demolished. Satellite dishes atop communications towers have been disabled and at least two military airfields in the Iraqi capital were crippled, the journalists said.

The bombing also appeared to leave a strong psychological scar on Iraqi civilians. "Even in the bomb shelters, the mood changed literally overnight," said Nigel Baker, a British television producer.

Anthony Massey, another British producer who left Baghdad yesterday, said: "The city appears virtually undamaged because of the accuracy of the cruise missile . . . But it is completely deserted."

The Iraqi parliament's speaker, however, said hundreds of thousands of weapons had been distributed to Baghdad residents, turning the capital into "a jungle of fighters and trenches."

On Capitol Hill, the House voted 399 to 6 to approve a non-binding resolution expressing support for U.S. troops in the gulf and commending the "efforts and leadership" of Bush as commander-in-chief. The Senate approved an identical resolution on Thursday.

In Washington, bomb threats, suspicious packages and abandoned cars had police responding to dozens of locations throughout the District. Dogs trained to detect explosives were taken through several buildings that were evacuated. Nothing was found.

The State Department warned Americans early today to be careful traveling to Thailand and said there had been "a credible threat involving possible terrorist action in Bangkok" in the next 48 hours against U.S., Israeli, British and Australian installations.

Staff writers Nora Boustany in Jordan; Jackson Diehl in Jerusalem, and Ann Devroy, Helen Dewar, Barton Gellman, David Hoffman, Tom Kenworthy, George Lardner Jr., Bill McAllister and R. Jeffrey Smith in Washington contributed to this report.