A NATO bombing blitz, which the alliance insisted was not aimed at Moamer Kadhafi, rocked Tripoli on Tuesday, as rebels in besieged Misrata claimed to be pushing back the Libyan strongman's forces.

The United Nations, meanwhile, said the offensive launched by Kadhafi's forces was paralysing the oil-rich nation and causing the population to suffer widespread shortages of essential goods.

The blasts came after NATO chief Anders Fogh Rasmussen said time was running out for Kadhafi.

He said Kadhafi "should realise sooner rather than later that there's no future for him or his regime."

Witnesses said the latest bombardment hit targets near Kadhafi's compound, but the mission's chief operations officer, Brigadier General Claudio Gabellini, denied that aim had been to take out the Libyan leader.

"All NATO targets are military targets, which means that the targets we've been hitting, and it happened also last night in Tripoli, are command and control bunkers," Gabellini told reporters.

"NATO is not targeting individuals," he said via videolink from his headquarters in Naples, Italy.

Asked whether Kadhafi was still alive, the Italian general said: "We don't have any evidence. We don't know what Kadhafi is doing right now."

He added later: "To tell you the truth, we are not really interested in what he's doing. Our mandate is to protect civilians from attacks or from the threats of attacks, so we are not looking after individuals."

Kadhafi had surived a similar NATO bombing on May 1 in Tripoli, which killed his second-youngest son, Seif al-Arab, and three of his grandchildren.

The rebels said they had driven Kadhafi's forces back from around Misrata, which has been under loyalist siege for some two months, and were poised to make another thrust.

After heavy clashes, the rebels controlled a stretch of coast road west of Misrata, their last major stronghold in the west, prompting thousands to flee.

The correspondent said there were some five hours of "ever intensifying fighting," with Kadhafi forces using snipers and mortars, tanks and anti-aircraft weapons, before they withdrew, leaving weapons and ammunition behind.

Haj Mohammed, a rebel commander, said "every day we manage to advance along the coastal road toward Zliten. Yesterday 15 kilometres (10 miles), today only two, but the advance is unstoppable."

Rebels were using shipping containers to shield themselves from loyalist fire, and bulldozers were pushing them forward as the advance continued.

Ahmad Hassan, a rebel spokesman in Misrata, said the insurgents had also "liberated" areas south and east of the city, killing many Kadhafi troops and seizing a large amount of weapons. Eighteen rebels and civilians were wounded.

The rebel claims could not be immediately verified.

Gabellini said NATO had struck more than 30 military targets in and around Misrata since May 2, including a dozen main battle tanks, three rocket-launcher systems, three self-propelled artillery pieces and 15 ammunition storage sites.