The BBC's Ben Brown says the rebels have made gains because of allied air raids
Libyan rebels backed by extensive allied air raids have seized control of the frontline oil town of Ajdabiya from Colonel Muammar Gaddafi's forces.
Insurgents have been celebrating amid the ruins of tanks and artillery pieces left behind after air strikes.
Gaddafi loyalists seized the town last week as they advanced east to quell an uprising which began in mid-February.
A Libyan minister said the army had left the town after the "heavy involvement" of Western forces.
The rebel breakthrough came after a seventh night of bombardment by allies enforcing a UN-mandated no-fly zone.
British RAF Tornado aircraft have been firing Brimstone guided missiles at Col Gaddafi's forces in recent days around Ajdabiya, a town of about 100,000 people.
The BBC's Ben Brown in Ajdabiya says those strikes seemed to be even heavier overnight.
Gaddafi 'promotes everyone'
He counted about two dozen Libyan government tanks, armoured vehicles and artillery pieces which have been either abandoned or destroyed at the eastern gate of the town.
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Analysis
Ben Brown
BBC News, Ajdabiya
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We're here by the eastern gate and the rebels have definitely taken that. They're saying they've also taken the western gate and the whole town, which they are combing street by street. Behind us there are jubilant rebels who say they've scored a decisive victory against the Gaddafi forces.
According to the insurgents, the Gaddafi forces have scattered in all directions, and the rebels are giving chase. It's a huge morale boost to the rebels but they couldn't have done it without coalition air power.
The rebels don't have very sophisticated weaponry, command structure or discipline. There have been a series of massive coalition air strikes through the night by coalition planes which have destroyed Gaddafi tanks and armoured vehicles.
The rebels are saying they will move west to their next target, Brega. Ultimately they're saying they will go to the capital Tripoli, but that still seems a long way off.
There is even more wrecked weaponry at the western gate and lots of bodies of pro-Gaddafi fighters, our correspondent has been told.
People have been standing on abandoned government tanks, firing guns into air, dancing in the streets and blaring car horns, he adds.
Some of them chanted "Thank you, Obama", "Thank you, Cameron" - references to the US president and British prime minister.
The rebels say they are going through the town street by street trying to make sure there are no government fighters or snipers left.
Reuters news agency, which earlier said the town's western gate was still in the hands of pro-Gaddafi forces, later quoted a Libyan government official as admitting they had abandoned the town.
"They [Western forces] were heavily involved, so the Libyan armed forces decided to leave Ajdabiya this morning," Khaled Kaim, a deputy foreign minister, told reporters.
Overnight strikes by international forces also reportedly hit an air base on the outskirts of Misrata, a rebel-held city further west which pro-Gaddafi forces have been shelling.
A rebel spokesman in the city told Reuters on Saturday that the government assault had eased as a result.
Large explosions were also heard in the Libyan capital Tripoli on Saturday morning.
Witnesses said a military radar site was set on fire in that city's suburb of Tajura, a previous target of the air raids.
In his weekly address, US President Barack Obama said that the "clear and focused" military mission in Libya was succeeding.
"Make no mistake, because we acted quickly, a humanitarian catastrophe has been avoided and the lives of countless civilians - innocent men, women and children - have been saved," he said.
Col Gaddafi is meanwhile said to have ordered a universal promotion for everyone in the army and police, and proposed arming civilian volunteers.
The BBC's Kevin Connolly in the eastern rebel stronghold of Benghazi says the administration's latest move smacks of desperation
