National Transitional Council (NTC) troops remained in the central police headquarters to which they retreated 2km on Thursday under heavy fire, an AFP correspondent reported.
The defiant Gaddafi diehards in the Dollar and Number Two residential neighbourhoods in northwest Sirte have been staging a fierce last stand that has put paid to NTC hopes of a swift mopping-up operation.
"Yesterday evening, we used artillery cannon to shell the neighbourhoods," Nasser Moghassabi, a frontline field commander with the Martyrs of Free Libya Brigade told AFP.
"The situation today remains the same. We are still surrounding the two neighbourhoods."
He said scouts had been sent in, "and very soon we will decide on the next plan of action."
NTC commanders said on Thursday the Gaddafi loyalists were cornered within about two square kilometres of the city.
Four pro-NTC fighters were killed on Thursday, including two by friendly fire, and another 40 were wounded, mostly by snipers, said Rawad Friwan, a surgeon at a field hospital on Sirte's western outskirts.
"There are still 500 pro-Gaddafi fighters in Sirte and our forces today arrested 15" of them, said Fayisal Ahmed Bringo, a new regime fighter.
NTC field commander Beloun al-Shaari of the Martyrs of the Mountains Brigade told AFP the strategy was "to close in inch by inch".
"Around 800 to 1 000 people are still in the area. Many of them are civilians which is making it a bit difficult for us to launch a big attack, but God willing, by tomorrow [Friday] we should be in control of that area," he said.