|Al Jazeera's Zeina Khodr reports from the frontline
The latest assault in the ongoing battle for Sirte, the hometown of former Libyan leader Muammar Gaddafi, is currently under way, with Libyan fighters undertaking a major operation to try to end a three-week standoff.
Commanders for the National Transitional Council said on Friday that the operation marked the final push to take the coastal city from Gaddafi loyalists.
Colonel Ahmed El-Obeidi, an NTC commander, said that NTC forces were advancing on Sirte from all directions and hoped to soon capture the city.
Medics said at least 12 anti-Gaddafi fighters had been killed and more than 125 others injured in the assault.
Ahmed Mohammed Abu Oud, the administrator of a nearby field hospital, said four ambulances had been destroyed by fire from Gaddafi forces, and two ambulance workers wounded.
Al Jazeera's Zeina Khodr, reporting from the frontline, said NTC fighters were trying to advance into the city centre, targeting the Ouagadougou conference hall where Gaddafi used to receive world leaders.
"Anti-Gaddafi fighters are at the perimeter of the hall, which is a stronghold of Gaddafi loyalists," she said.
"But the loyalists holed up inside are putting up a fierce fight. According to [NTC] fighters, most of the men inside are 'wanted criminals' so it's not in their interest to lay down their arms."
There were also particularly violent clashes around and inside the university, near the city centre, and in the Mauritanian Quarter.
Sirte, 400km southeast of Tripoli, is the most important of the pro-Gaddafi cities that are still holding out against Libya's new rulers. The two sides have been trading artillery, tank and mortar shelling.
Plumes of black smoke could be seen rising from several points in the city, amid the sound of machine gun fire and explosions.
NATO fighter jets flew overhead, but there were no reports of air strikes.
Our correspondent said that while thousands of civilians had left over the past three weeks, some were still trapped inside.
"We spoke to civilians as they left and while some said they had been trapped inside the city or even prevented from leaving by Gaddafi loyalists, there are some that did not want to leave.
"This is a Gaddafi stronghold and many of the civilians who have left expressed resentment against anti-Gaddafi fighters and NATO as well."
NTC forces have besieged Sirte since September 15, but have not managed to penetrate the heart of the city because of fierce resistance.
Salah al-Jabo, an NTC field commander, said his men were trying to evacuate the Ibn Sina hospital near the Ouagadougou centre.
Jabo estimated there were only about 800 pro-Gaddafi fighters left in the entire city, and that the area under their control had been reduced to roughly 20sq km.
At the same time, he said there were only about 400 civilians left in Sirte.
That figure was impossible to confirm, but an AFP reporter said that only a trickle of refugees had come out on Thursday and the previous day, compared with dozens if not hundreds of cars in previous days.
Many among the thousands of residents who have escaped complained that the biggest danger was not Gaddafi loyalists but the bombs that drop from the sky and the ones the NTC fighters lob into their Mediterranean port city.