EASTERN SAUDI ARABIA, JAN. 21 (MONDAY) -- U.S. Patriot air-defense missiles intercepted nine Iraqi Scud missiles fired at key Saudi cities and military installations Sunday night and early this morning in a dramatic indication that Iraqi President Saddam Hussein has managed to keep some of his offensive capability intact despite intensive air raids by allied warplanes.

Troops on the ground watched as Patriot missiles arched into the dark skies and collided with incoming Scuds, which exploded in a rain of fiery debris.

"All of a sudden, a Patriot took off and impacted with the incoming missile," said Coast Guard Lt. Cmdr. Paul Milligan, who was standing guard during the first of two attacks launched toward the Persian Gulf city of Dhahran. "There was a burst of light, then burning debris fell to the ground."

Military officials said Patriot missiles intercepted five Scuds rocketing toward Dhahran and another four aimed toward the capital city, Riyadh, in central Saudi Arabia. The 10th Scud was reported to have landed in the Persian Gulf.

The booms of the Patriot missiles exploding out of their launchers echoed across both cities.

In Dhahran, air raid sirens sent many residents racing for bomb shelters and scrambling to pull on gas masks two times during the night, usually just as the first missile from the two separate volleys exploded over the desert. Readings taken by U.S. military specialists near the areas where the Scuds were intercepted detected no chemical or nerve agents, according to military officials.

Several reporters saw a crater about 10 feet deep and 15 feet wide near the old Riyadh airport, now used as a military air base, correspondent Caryle Murphy reported from Riyadh. It was unclear what created the crater, but damage attributed to the explosive collisions of Patriots and Scuds was seen in several places in both cities.

An office building in front of the crater in Riyadh and a smaller building next to it were damaged, apparently by an explosion. Windows in shops, a pharmacy and a bank in a two-block area were shattered.

The attacks directed against Dhahran and Riyadh were launched just hours after Gen. H. Norman Schwarzkopf, commander of the U.S. forces in the Persian Gulf, emphasized the massive effort undertaken by the allied forces to comb the vast expanses of western Iraq for missiles aimed at Israel.

"The numbers have jumped around so much that it is almost impossible to predict how many {mobile missile launchers} they had to begin with and how many are left now," Schwarzkopf said during one of several interviews he conducted with U.S. television networks Sunday morning.

Increasing the uncertainty about how much punch Iraq has left after four days of war, Saddam said in a radio address that his arsenal had "so far only been used in part. Our ground forces have not entered the battle so far, and only a small part of our air force has been used."

Saddam said that "in the coming period, the response of Iraq will be on a larger scale."

As the war against Iraq entered its fifth day this morning, U.S. and allied air forces met with varying degrees of resistance from antiaircraft artillery fire at targets in Iraq and Kuwait, prompting some military leaders to conclude that the Iraqi forces may be holding back some of their ammunition for future stages of the war.

In addition to the hunt for the elusive Scuds, there were other indications that the air phase of this war could last for weeks and that it will take ground combat to wrest Kuwait from the grip of Iraqi troops.

Some field commanders say they believe the Iraqis may be moving some of their military operations, including those of Saddam, into heavily populated residential areas as a shield against potential attack. American military officials have said repeatedly that they are attempting to avoid damage to civilian neighborhoods in their air assaults.

Allied warplanes have been forced to make repeated bombing runs at Iraqi communications facilities as Saddam's military continues to erect new communications equipment to replace damaged relay centers, according to military leaders.

In London, British officials said the United States and Britain agreed that more air strikes are needed and that a ground attack could not take place for some time, the Reuter news agency reported.

"A lot more is still to be done with air strikes. We are not talking about ground warfare for some time yet," one British official said.

While antiaircraft fire has diminished in some areas of Iraq and Kuwait, pilots say it has intensified since the first night of the war in other areas. U.S. forces suffered the heaviest aircraft losses for a 24-hour period of the war Sunday when three planes were brought down, bringing the total number of aircraft downed by battle damage to eight. One other plane crashed because of mechanical problems. U.S. officials have emphasized, however, that losses remain extremely light in proportion to the huge number of missions flown.

Although military leaders say U.S. planes have successfully hit 80 percent of their targets, the military increased the number of missions from under 2,000 a day to about 2,300 on Day 4 of the war.

Schwarzkopf explained that the warplanes were "rehitting" some targets and that the military is discovering an "ever-expanding list" of new targets. Allied warplanes have conducted about 7,000 missions against Iraqi targets since the war began. Not all of those missions, or sorties, involve attack aircraft; many are flights by escort planes and electronic warfare aircraft.

The military has been pummeling Iraq's Republican Guard forces with B-52 bombers and other warplanes constantly, but Schwarzkopf and other field commanders warned that aerial assaults alone are unlikely to dislodge Saddam's 540,000-member fighting force assembled in Kuwait and southern Iraq.

"You have to caution against being over-optimistic," said Schwarzkopf. "Armored divisions are tough to blow out under the best of circumstances." He warned that it is not an effort that can be undertaken quickly and said "a lot of things have to be accomplished between now" and the start of the land assault.

Military officials originally estimated that ground combat would begin within two to four weeks of the start of the air attacks against Iraq, which commenced Thursday morning.

Since the start of the war, U.S. Marine Cobra helicopter gunships have been pelting Iraqi forward observation posts that could be used to guide artillery fire against troops across the border in Saudi Arabia.

Since the bombing campaign on Iraqi forces began, Iraqi troops have turned small-weapons fire and a few surface-to-air missiles against the attack Cobra gunships.

More recently, however, the pilots have drawn little anti-aircraft fire of any kind, and most missions have been flown unopposed. The helicopter pilots expressed surprise Sunday that the enemy forces have offered only token resistance and are concealing their weapons and hunkering down instead, because Saddam's troops along the Kuwaiti-Saudi border are known to have arsenals of surface-to-air missiles and multiple-barrelled antiaircraft cannon -- both considered effective against the Marines' relatively slow-moving Cobras.

"We expected to see a lot more," said Capt. Doug Griffith, 27, of San Antonio, Tex. "We're ready for them, but they're just not coming."

Pilots and field commanders have speculated that the Iraqis may be conserving firepower in an effort to inflict a higher number of casualties once the allied ground attack begins.

"{Saddam} knows that will have the biggest effect on our morale and the reaction back home if we start taking casualties out here," said Griffith. Other pilots said they are fearful that Saddam is holding chemical weapons in reserve.

While most of the Iraqi observation posts have been set up in bunkers dug into the sand, the pilots said other positions have been established in civilian buildings, raising the likelihood of civilian casualties and complicating the mission of pilots assigned to take out the posts.

"We're trying to liberate the country," said Capt. Travis Allen, a 32-year-old Texan who has been flying missions against the observation posts. "We don't want to go up there and kill the inhabitants."

Meanwhile, on the Saudi side of the border where Iraqi artillery fire has sporadically pounded the desert near a Marine encampment, the first Purple Heart award for a serviceman or woman wounded in combat in Operation Desert Storm was ordered for a Marine wounded by shrapnel given off by the Iraqi artillery.

Washington Post staff writers Stephen C. Fehr and Guy Gugliotta contributed to this article.

Number lost.....................Type

Two................Navy A-6E Intruder bomber

One................F/A-18 Hornet fighter-bomber

Two................F-15E Eagle dual role attack/air

...................superiority fighter

One................OV-10 light forward air control plane

One................F-4G Wild Weasel electronics warfare fighter


Four.....................Tornado GR1/ground-attack planes


One......................Tornado fighter


One......................A-4 Skyhawk


Ten.....................MiG-29 fighter

One.....................MiG-23 fighter

Four....................Mirage F-1 fighter/attack aircraft