Interim government forces in Libya say they have seized a convention centre, university and the main hospital in Sirte while making head way in another Moammar Gadhafi stronghold Bani Walid.
A commander of the forces backing the National Transitional Council (NTC) told Reuters that 15 fighters loyal to Gadhafi were captured inside Sirte's Ibn Sina Hospital on Sunday.
However, Saleh Mustafa said several Gadhafi loyalists were able to flee, including some who were disguised as doctors.
He added NTC fighters were trying to evacuate the sick and wounded.
Mustafa Abdul-Jalil, head of the governing National Transitional Council, said Sunday that anti-Gadhafi fighters have also made gains in Bani Walid, southeast of the capital.
"I do believe, God willing, that the liberation of these cities will happen within this week," Abdul-Jalil told reporters in Tripoli.
He said that revolutionary forces in Sirte are now cleaning out pockets of resistance.
Witnesses in Sirte said Gadhafi forces had been using the hospital buildings to launch mortars and rocket-propelled grenades. A huge plume of black smoke was visible over Sirte on Sunday morning as revolutionary forces continued their assault on Gadhafi's hometown, 400 kilometres southeast of the capital, Tripoli.
Meanwhile, scores of civilians continue to leave the area. Cars could be seen queuing at the first roadblock after the western front line on Sunday morning with families making their way out of the city.
Gadhafi loyalists driven from Bani Walid airport
Rebel forces began a major attack on Friday after a three-week siege from the outskirts of the coastal city, during which they said they were giving civilians time to flee.
The inability to take Sirte, more than six weeks after the NTC capture of Tripoli, has stalled efforts by Libya's new leaders to set a timeline for elections and move forward with a transition to democracy.
Gadhafi forces still control Bani Walid in the central mountains, but the council says Sirte is more important stragetically because it's located on the coast and divides Libya into east and west.
In Bani Walid, advancing fighters drove Gadhafi forces out of the airport, said Abdullah Kenshil, who led failed talks for the revolutionaries in search of a peaceful surrender of the city.
"The takeover of Bani Walid is imminent," he said. "The fighters are only one kilometer from the heart of Bani Walid."
He claimed that Gadhafi's son Seif al-Islam was seen on Saturday distributing cash to his loyalists in Bani Walid.
"We are 100 per cent sure that he is inside, at least until last night," Kenshil said.