Libya: Fierce fighting in Gaddafi stronghold Sirte
There has been heavy fighting in the Libyan city of Sirte, where armed supporters of the transitional authorities are facing strong resistance from Gaddafi loyalists.
A BBC correspondent on the outskirts of the city says the two sides have been exchanging machine-gun fire, rockets and artillery shells.
Many thousands of civilians remain in Sirte, east of the capital, Tripoli.
Humanitarian agencies have expressed concern about the conditions they face.
Sirte remains one of the final strongholds of supporters of the beleaguered colonel, with Bani Walid 250km (155 miles) to the west the only other major city holding out.Urban snipers
Hundreds of National Transitional Council (NTC) troops are inside Sirte, but snipers were holding off an advance into the centre of the city, news agency Reuters reported.
At the scene
If there was any doubt as to whether the pro-Gaddafi forces within Sirte were going to resist this offensive by the National Transitional Council, the proof is here.
We are on the coast road which enters Sirte from the north, in a villa where a number of the former rebel troops are sitting behind a wall, taking cover from what has been a very fierce fight less than a mile ahead of us. Earlier in the day, there were tanks and rockets exchanging fire on the other approach to the city.
It is hard to know exactly how many of the pro-Gaddafi elements there are, but certainly there are snipers and they are firing rockets. This is descending into the street-by-street fight that people were concerned about, particularly for those civilians who are still inside.
For a second day, anti-Gaddafi forces were pinned down at a roundabout about 2km (1.5 miles) from the city centre, it said.
"Gaddafi forces have placed a lot of snipers around the roundabout and it is not easy for us to advance forward until we get rid of the snipers," Ahmed Saleh, an NTC fighter there, told Reuters.
The agency said explosions of artillery rounds and exchanges of small arms fire could be heard, and Nato warplanes were flying overhead.
There have also been clashes at the port.
Humanitarian agencies warn civilians inside Sirte and Bani Walid have appealed for help, saying medical supplies and food are running short.
Once the fighting gets underway and both sides establish front lines, there will be a good indication of whether Sirte will fall quickly or whether it will descend into dangerous urban warfare which would kill and injure many civilians and soldiers, says the BBC's Alastair Leithead in the city.
The fire power and determination of the new Libyan government's army will take Col Gaddafi's home town, he says, but with propaganda saying the rebels want revenge, those defending Sirte may fight to the death thinking they have nothing to lose.