Western airstrikes Wednesday hammered Libyan government tanks and artillery that were shelling the rebel-held city of Misurata, residents reported, but sniper fire from downtown rooftops continued to claim civilian lives on the fifth day of U.S. and allied military intervention.

The strikes, aimed at breaking the siege of Misurata by troops loyal to Libyan leader Moammar Gaddafi, destroyed some tanks and forced others to flee the city, temporarily halting the bombardments that have killed dozens of people in recent days, residents said.

The chief of staff for the Western joint task force carrying out the strikes confirmed Wednesday that the coalition has targeted pro-Gaddafi forces attacking Misurata with tanks, artillery and rocket launchers. But he declined to provide details of the strikes and said the regime forces are not yet standing down. As a result, he said, coalition strikes “will continue.”

In Tripoli, several loud explosions followed by bursts of antiaircraft fire were heard late Wednesday, the fifth consecutive night of airstrikes against the capital.

In eastern Libya, rebels continued to battle Gaddafi’s forces for control of the strategic city of Ajdabiya, which was captured by the loyalists last week during an offensive against the rebel capital of Benghazi, Libya’s second-largest city. The initial strikes by Western coalition forces enforcing a U.N. no-fly zone forced Gaddafi’s forces to retreat from Benghazi, but the loyalists have remained entrenched in Ajdabiya about 100 miles to the south.

Fierce fighting was also reported in Zintan, a small town about 100 miles southwest of Tripoli that has been under siege by loyalist forces armed with tanks, artillery and rockets.

The most dire humanitarian situation appeared to be unfolding in Misurata, Libya’s third-largest city about 130 miles east of Tripoli, where coalition warplanes struck Libyan tank positions on the city’s outskirts early Wednesday. The attacks brought a temporary respite from the fierce fighting that had raged for the previous six days as Libyan forces attempted to retake the town from rebels who have controlled it for the past month.

Loyalist tanks resumed their bombardment of the city Wednesday night after a daylong lull. Following the pre-dawn airstrikes, the tanks retreated from the city center, although a sniper continued to terrorize residents, killing at least four, according to a doctor in the Misurata’s hospital.

But after nightfall, the tanks returned and began indiscriminately shelling the city center, including the area around the hospital, said the doctor, who spoke by telephone on condition of anonymity because he fears being targeted by Libyan forces.

“They are shelling everywhere,” he said. One shell landed near the hospital, he said, and two people were hurt.

The doctor said conditions at the hospital were critical, with patients being treated on the floor and all medical supplies and medicines in short supply. The hospital has a generator, but fuel is running low and water supplies have been cut off, he said.

He called on the coalition to provide air cover for ships to deliver humanitarian aid to the port, which is functioning.

“Every minute counts,” he said. “It could mean more people are dead.”

Earlier, a Misurata resident who gave his name only as Saadoun told Reuters news agency by telephone that people were “more optimistic” after the Western airstrikes began to relieve the pressure on the besieged city surrounded by Gaddafi’s forces.

“These strikes give us hope, especially the fact they are precise and are targeting the [Gaddafi] forces and not only the bases,” Reuters quoted him as saying. He said there had apparently been two strikes targeting locations in the southwestern part of the city where pro-Gaddafi forces are positioned.

The news agency quoted another resident as saying the strikes hit an air base and military training college that Gaddafi’s forces had been using to launch attacks.

The coalition strikes did not stop snipers loyal to Gaddafi from shooting people from rooftops in the center of Misurata, apparently targeting people trying to gain access to a hospital where hundreds of wounded people are being treated, news agencies said.

Among the fatalities were at least three people who were shot near the hospital, Reuters reported.

Aboard the USS Mount Whitney, the flagship for U.S. naval forces in the Mediterranean, Rear Adm. Gerard P. Hueber told Pentagon reporters by audio link: “We are putting pressure on Gaddafi’s ground forces that are attacking civilian populations in cities.” As long as those forces keep fighting in Ajdabiya and Misurata, he said, “that pressure from Joint Task Force Odyssey Dawn coalition partners will continue.”

Hueber, the task force chief of staff, said strikes are aimed at interdicting “mechanized forces or artillery” besieging the cities, as well as cutting off their supply lines and disrupting their command and control.

“We have no indication that the Gaddafi forces are adhering to the United Nations Security [Council] resolution 1973, and that is why we continue to pressurize those forces,” Hueber said, referring to the U.N. resolution that established the no-fly zone over Libya.

Reiterating demands that President Obama made last week and that U.S. forces have made part of their mission, Hueber said: “Gaddafi’s forces must cease fire, all attacks against civilians must stop, forces must have stopped advancing on Benghazi and be pulled back from Ajdabiya, Misurata and Zawiyah, and humanitarian assistance must be allowed to reach the people of Libya.”

Hueber said the no-fly zone is now in force across the entire Libyan coast and that Gaddafi’s air force has stopped flying. He said there have been “no reports of civilian casualties” inflicted by coalition forces as part of their mission to protect Libyan civilians.

“Our efforts have been going well,” Hueber said, but he declined to predict when the campaign would end. The strikes against Gaddafi’s forces have taken place “outside” Misurata and Ajdabiya, he said, and the loyalists “are making incursions into the cities and targeting population centers in those cities” with tanks, artillery and rockets.

The coalition has communicated with Gaddafi’s forces to tell them “what they need to do to comply” with the U.N. Security Council resolution, but there has been “no indication” yet of such compliance, Hueber said.

Four days of allied strikes have battered­ Gaddafi’s air force and largely destroyed his long-range air defense systems, a top U.S. commander said Tuesday. But there was little evidence yet that the attacks had stopped regime forces from killing civilians or shifted the balance of power in favor of the rebels.

The Libyan military’s attacks and the mounting civilian deaths call into question whether the internationally imposed no-fly zone can achieve its goal of protecting civilians, let alone help loosen Gaddafi’s grip on power. It seemed unlikely that the coalition, which has argued in recent days over the scope and leadership of the allied mission, would countenance a significant escalation.

Late Tuesday, Gaddafi made his first televised appearance since the bombing campaign began, delivering a defiant address to supporters at his Tripoli compound, which was struck by Tomahawk missiles a few days earlier. “I am here, I am here, I am here,” he said, as celebratory gunfire echoed across the city. “We will win. We will be victorious in this historic battle.”

President Obama, meanwhile, sought to shore up support for the international mission, saying that the U.S. and allied efforts to halt advances by Gaddafi’s forces had “saved lives.”

“In Benghazi, a city of 700,000 people, you had the prospect of Gaddafi’s forces carrying out his orders to show no mercy,” Obama said at a news conference while in San Salvador. “That could have resulted in catastrophe in that town.”

Hours earlier, a top U.S. military official had touted the limited gains that allied forces had made over the course of the four-day-old military intervention.

Since the bombing began Saturday, U.S. and allied forces have launched 162 Tomahawk missiles and conducted more than 100 attacks with precision-guided satellite bombs, said U.S. Navy Adm. Samuel J. Locklear III, commander of the allied task force charged with enforcing the U.N. resolution that authorized action in Libya.

But he conceded that the airstrikes have been unable to halt attacks by Libyan government forces against civilians.

“They are conducting attacks against civilians in Misurata in violation of the Security Council resolution,” Locklear said Tuesday. He added that allied commanders were “considering all options” to halt attacks by Libyan forces but declined to provide specifics about any future military actions.

A doctor at a Misurata hospital said Tuesday that about 80 people had been killed in the city since the adoption Thursday of the U.N. resolution, which called for a halt to attacks on civilians. Among the 12 said to have died Tuesday was a family of six; a tank shell hit their car. The doctor said that he had stopped counting the injured, that patients are being treated on the floor and that the hospital is running out of almost all medicines and supplies.

“This no-fly zone doesn’t mean anything to us because Gaddafi only had a few planes and they were doing nothing,” the doctor said Tuesday, speaking by telephone on the condition of anonymity because he fears Libyan forces may soon retake the city. “We need a no-drive zone because it is tanks and snipers that are killing us.”

Gaddafi loyalists, who launched a major assault on Misurata just hours before the U.N. Security Council vote, secured several neighborhoods on the outskirts of the city, but rebels were holding out in the city center. To halt the Libyan government’s advance, allied forces would probably have to launch airstrikes in densely populated urban areas.

Question of civilian toll

In Moscow, U.S. Defense Secretary Robert M. Gates said Tuesday that the pace of attacks would wane in the days ahead as the United States hands over responsibility for maintaining the no-fly zone to its allies and the number of clear targets diminishes.

Meanwhile, there were indications that international support for the coalition effort is beginning to flag, with China joining Russia in calling for a cease-fire to avert feared civilian casualties. China, like Russia, abstained from voting on the U.N. resolution.

“The U.N. resolution on the no-fly zone over Libya aimed to protect civilians,” Chinese Foreign Ministry spokeswoman Jiang Yu told reporters at a news briefing. “We oppose abuse of force causing more civilian casualties.”

U.S. and other coalition officials dispute Libyan assertions that the strikes have caused civilian deaths. “It’s perfectly evident that the vast majority — if not nearly all — of civilian casualties have been inflicted by Gaddafi,” Gates told reporters after meeting with Russian Defense Minister Anatoly Serdyukov. “We’ve been very careful about this.”

Britain’s Channel 4 TV reported that six villagers were injured by American troops, who apparently opened fire during the rescue of two U.S. crew members forced to eject over eastern Libya when their F-15 fighter jet malfunctioned and crashed overnight Monday. Among the injured civilians was a young boy who is likely to lose a leg, Channel 4 said.

Locklear declined to comment on the report and said an investigation had been launched into why the jet crashed. He said one of the downed aviators had been rescued by rebels, who “treated him with dignity and respect” before handing him over to the U.S. military. U.S. forces rescued the plane’s weapons operator, the military said.

Clinton’s comments

Secretary of State Hillary Rodham Clinton suggested Tuesday that the Libyan leader and some members of his inner circle might be searching for a way out of the country — and the conflict.

“We’ve heard about other people close to him reaching out to people that they know around the world — Africa, the Middle East, Europe, North America, beyond — saying what do we do? How do we get out of this? What happens next?” Clinton said in an interview with ABC News.

But at least in Tripoli, the government appears to be in firm control nearly a month after the last major protests were crushed by security forces using live ammunition.

On Tuesday, Libyan government officials took journalists to see a cluster of bombed warehouses struck the previous night at a central harbor that appeared to have housed military hardware.

In one warehouse, four mobile missile launchers had been destroyed by a direct hit, along with a multiple-barreled rocket launcher. Three Soviet-made surface-to-surface missiles were unscathed, but officials said they were used only for training. Libyan navy Capt. Abdul Bassit told reporters that no one had been killed in the attack because officials had suspected the site would be targeted and had evacuated it.

Jaffe and Branigin reproted from Washington. Staff writer Craig Whitlock in Moscow and correspondent Keith B. Richburg in Beijing contributed to this report.