Five civilians were killed in a 30-minute barrage of shelling that heavily damaged a factory for dairy products and sent up a thick column of black smoke, a doctor said. A human rights group has accused the Gadhafi regime of using cluster bombs in Misrata — munitions that can cause indiscriminate casualties and have been banned by most countries. The Libyan government denies the charge.

In eastern Libya, fierce fighting left seven rebels dead, 27 wounded and four missing as the anti-Gadhafi forces sought to push toward the strategic oil town of Brega, according to Mohammed Idris, a hospital supervisor in the nearby city of Ajdabiya. The battle took place on a road halfway between Ajdabiya and Brega.

Frustration was growing among residents in Misrata, where Gadhafi's troops have intensified their long siege of the city in recent days. The doctor sharply criticized NATO for failing to break the assault with its month-old campaign of airstrikes.

"We have not seen any protection of civilians," the doctor said. "NATO airstrikes are not enough, and the proof is that there are civilians killed every day here," he said.

The theme was echoed in the rebel stronghold of Benghazi, where spokesman Abdel-Hafidh Ghoga told a news conference: "There's no more room for hesitation or for not standing with determination against what is happening in Misrata and other Libyan cities, because the destruction that Moammar Gadhafi is causing in Libyan cities is great and extensive."