Forces loyal to the interim government battled for control of Sirte on Thursday.
The city is Muammar Gaddafi’s birthplace and one of the last pockets of resistance against the former rebel movement, the National Transitional Council.
A spokesman for the NTC said one of its men was killed in the fighting with Gaddafi loyalists. Twenty were injured.
Pro-NTC forces earlier raised their flag on the outskirts of Sirte as they entered the city through its suburbs in the south and west.
They said they came under fire from Gaddafi’s men, who shelled them with mortars and other heavy artillery.
There were unconfirmed reports that NATO struck a south-bound convoy of pro-Gaddafi armoured vehicles about 50 kilometres from Sirte.
The whereabouts of the toppled Libyan leader, however, remain unknown.