AJDABIYA, Libya — International airstrikes forced Moammar Gadhafi’s forces to withdraw tanks that were besieging a rebel-held western city today, residents said, while people fleeing a strategic city in the east said the situation was deteriorating amid relentless shelling.

Western diplomats, meanwhile, said an agreement was emerging about how NATO would take responsibility for a no-fly zone over Libya after the United States, which has effectively commanded the operation until now, reiterated that it was committed to the transition.

NATO warships were to begin patrolling off Libya’s coast today to enforce the U.N. arms embargo.

The international coalition continued airstrikes and patrols aimed at enforcing a no-fly zone and protecting Libyan civilians early today, but the report that Misrata was targeted could not immediately be confirmed.

U.S. Navy Adm. Samuel J. Locklear, the on-scene commander, said Tuesday the coalition was “considering all options” in response to intelligence showing troops were targeting civilians in the city, 125 miles southeast of Tripoli.

A doctor in Misrata said the tanks fled shortly after the airstrikes began around midnight, giving the city a much-needed reprieve after more than a week of attacks and a punishing blockade. The city is inaccessible to human rights monitors or journalists.

“There were very loud explosions. It was hard to see the planes,” the doctor said, speaking on condition of anonymity for fear of reprisals if Gadhafi’s forces take the city. “Today for the first time in a week, the bakeries opened their doors.”

He said the situation was better but still dangerous, with pro-Gadhafi snipers shooting at people from rooftops inside the city.

The airstrikes targeted the aviation academy and the lot outside the central hospital, which was under maintenance.

“Some of the tanks were hit and others fled,” he said. “We fear the tanks that fled will return if the airstrikes stop.”

The withdrawal of the tanks from Misrata was a rare success story for the rebels, who hold much of the east but have struggled to take advantage of the gains from the international air campaign, which appears to have hobbled Gadhafi’s air defenses and artillery and rescued the rebels from impending defeat.

Neither side has been able to muster the force for an outright victory, raising concerns of a prolonged conflict.