Libyan troops clash with pro-Gaddafi forces in Sirte
The forces of Libya's transition government have clashed with supporters of ousted leader Muammar Gaddafi in one of his last strongholds, Sirte.
Black smoke was seen rising from the coastal city after National Transitional Council (NTC) soldiers entered from both the west and east.
A BBC correspondent says NTC forces have moved swiftly towards the centre of Sirte, Col Gaddafi's birthplace.
It is not known if the colonel or his family members are in the city.
Sirte, one of two remaining bastions of support for Col Gaddafi, has fiercely resisted attempts by NTC forces to capture it over recent weeks.
NTC fighters advancing from the west say they have reached a roundabout about 1km (half a mile) from the city centre.
At the scene
From the east of Sirte, the advance today has been swift. After days of stalemate, the east gate fell and the NTC troops have pushed far along the road towards the city centre, outpacing the protection of the artillery and rockets which has been bombarding what's left of the pro-Gaddafi positions - now perhaps, just isolated groups of fighters.
There has been some return of fire, some injured but the momentum is carrying them forward.
This is Col Gaddafi's birthplace, his hometown. It's always been a hugely symbolic target for the NTC and it seems close to being won.
The question is how determined those Gaddafi loyalists are inside Sirte. How much more will they resist before the city goes the way of so many other towns and villages in Libya before it?
An NTC fighter inside the town, El-Tohamy Abuzein, told Reuters news agency that pro-Gaddafi snipers were firing from mosques and other buildings. "They're using the houses and public buildings," he said.
Medical sources told AFP news agency that two soldiers of the interim government had been killed.Tripoli blasts
The BBC's Alastair Leithead, who is with government troops on the eastern side of Sirte, says they have already pushed far along the road towards the city centre.
The soldiers have been exchanging rocket-fire with Gaddafi loyalists defending the city, our correspondent adds.
Government fighters tried to push into Sirte last weekend but were driven back by pro-Gaddafi forces entrenched in the city.
Nato aircraft hit targets in the Sirte area on Saturday, as part of its UN-mandated mission to protect civilians. Nato air strikes have played a major role in the conflict.
The NTC is also facing strong resistance in the only other remaining Gaddafi stronghold, Bani Walid to the south-east of Tripoli.
In the capital itself, explosions were heard on Saturday afternoon. Plumes of smokes were seen rising from the harbour area.
Officials later said it has been an accident at a military storage facility.
Also on Saturday, NTC chairman Mustafa Abdul Jalil said a new interim government would be announced within a week.
At UN headquarters in New York, Libya's interim Prime Minister Mahmoud Jibril gave his first address to the General Assembly.
He said a new democratic Libya was "coming to life" and reaching out to the international community.
Mr Jibril asked member states to unfreeze all of Libyan assets "to assure reconstruction and rehabilitation of the country".
Col Gaddafi went into hiding after Tripoli fell to NTC forces in August, six months into the uprising.
The whereabouts of the former leader - who ruled Libya for 42 years - are unknown. Many of his relatives and aides have taken refuge in neighbouring Algeria and Niger.
Meanwhile a report on the NTC's Qatar-based Libya TV criticised the Algerian authorities over an audio message broadcast by Col Gaddafi's daughter Aisha - who has fled to Algeria.
The message, which criticised the new Libyan government, was broadcast on Friday by a pro-Gaddafi TV channel in Syria.
Libya TV said Aisha Gaddafi should not be allowed to make political statements. She was granted entry in Algeria for humanitarian reasons.