BBC News with Fiona MacDonald

Forces of the interim authorities in Libya have encountered stiff resistance from the Gaddafi loyalists as they renewed their attack on the centre of the city of Sirte, one of the last pro-Gaddafi strongholds. Commanders said they've come under heavy sniper fire from rooftops in fierce street fighting. Our correspondent Jonathan Head is just outside the city.

The volunteer fighters on the government side have found it hard to keep up the momentum of the attack they launched against the centre of Sirte. Some units withdrew from their most forward positions overnight after encountering fierce resistance by well-armed Gaddafi loyalists. But they say they've held most of their gains and are massing again to renew the offensive.

They've had problems coordinating their advances, and some of the nearly 200 casualties they suffered on the first day were caused by their own forces either through accidents or through firing on each other. Civilians have continued to leave the town in small numbers, terrified by their ordeal and by what now awaits them, although pro-government fighters have tried to convince them they will be well treated.