Libya rebels have captured Misrata airport after a fierce battle with Muammar Gaddafi's troops, marking their first significant advance after weeks of being pinned back by the loyalists.

The airport of Libya's third city, which had been besieged for almost two months by Gaddafi's forces, fell to the rebels after fighting that raged through the night, said an AFP correspondent at the scene.

The rebels celebrated the victory by cheering in the streets and setting ablaze tanks left behind by Gaddafi  troops.

The capture of the airport is seen as significant as the city had been cut off from the outside world by Gaddafi's forces, with the port being the only route in or out of the city.

Rights groups have warned of a looming humanitarian catastrophe in the city of 500,000 people, who have been facing acute shortages of food and medical supplies.

Insurgent forces captured 40 Grad rockets from the regime troops, whose mortar fire injured 13 rebels, the correspondent said.

Inspired by the uprisings in other Arab nations, rebels have been fighting since mid-February to oust Gaddafi but have met with stiff resistance despite gaining a foothold in the eastern city of Benghazi.

A spokesman for the rebels' National Transitional Council in their main bastion of Benghazi in eastern Libya confirmed Misrata airport had been captured.

"We took full control of Misrata airport and pushed back Gaddafi forces around 15 kilometres from airport," said Abdel Busin.

"The airport is in our control but is not free because it is still within range of Grad rockets" fired by Gaddafi retreating forces.

Haj Mohammed, a Misrata rebel commander, had said on Tuesday that Gaddafi's forces were slowly being pushed back westwards from Misrata along the coastal road toward the town of Zliten.

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

Meanwhile, a volley of missiles struck east of the Libyan capital Tripoli on Wednesday after intense overflights by NATO-led aircraft, a witness said. There was no immediate confirmation from the Western alliance.

The munitions hits near Tajoura, a coastal town that was a focus of anti-government protests before a strong-armed crackdown by the authorities.

NATO said on Tuesday that since the alliance took over military operations on March 31 to protect civilians from pro-Gaddafi forces, jets have conducted almost 6,000 sorties, including more than 2,300 strike missions.

Bombs were not dropped during all of those missions, figures showed, as officials insisted again the raids were not aimed at killingGaddafi , who has ruled Libya for more than four decades.

"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," Brigadier General Claudio Gabellini told reporters on Tuesday.

"NATO is not targeting individuals," he said via videolink from the operation's headquarters in Naples, Italy.

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

Italian Defence Minister Ignazio La Russa said Gaddafi is a legitimate target if he is inside a military installation.

"If, for example, it's a place from which orders are being issued to strike against civilians then a raid is legitimate," he said in an interview with Il Messaggero Wednesday.

Italy's Foreign Minister Franco Frattini said Gaddafi has until the end of May to agree his exile before an arrest warrant from the International Criminal Court is issued against him.

"There are countries that in recent weeks have indicated... a willingness to welcome him," Frattini said in an interview with RAI public radio.

"It's clear that if there is an international arrest warrant it would be more difficult to find an arrangement for the colonel and his family," he said.

"This will happen by the end of May," he added.

UN chief Ban Ki-moon Wednesday urged Libya's Prime Minister Baghdadi Mahmudi to immediately stop attacks on civilians and called for an "end of fighting in Misrata and elsewhere."

"I told him the Libyan authorities must stop attacking civilians, I said there must be an immediate verifiable ceasefire negotiations towards the peaceful resolution of the conflict and unimpeded access to humanitarian workers," Ban told journalists.

The European Union decided to open an office in Benghazi in order to boost its assistance to the anti-Gaddafi movement.

The aim of the new office would be "to support civil society, to support the interim national council... to support security sector reform, to build on what the people ask us to," EU foreign policy chief Catherine Ashton told the European parliament.

"They want health and education, health-care, security on the borders, the kind of support we are able to give them and want to give them."

Her statement came the same day rebel leader Jibril was to meet in Washington with key US lawmakers, including senator John Kerry, a Democratic ally of the White House who chairs the Senate Foreign Relations Committee.

"The Foreign Relations Committee and the American people are eager to learn more about the opposition movement in Libya and Mahmud Jibril is well positioned to answer our questions," Kerry said in a statement Tuesday.

Sign up to our free newsletters

Get the best updates straight to your inbox:
Please select at least one mailing list.

You can unsubscribe at any time by clicking the link in the footer of our emails. We use Mailchimp as our marketing platform. By subscribing, you acknowledge that your information will be transferred to Mailchimp for processing.