Sirte was rocked by deadly street fighting on Friday in what troops from the new regime said was the final assault on Muammar Gaddafi's besieged hometown, with orders that they take it "today."

By mid-afternoon, however, sustained mortar, machinegun and sniper fire was preventing National Transitional Council forces from overrunning the Ouagadougou conference centre, a major bastion of pro-Gaddafi forces in the west of the city.

As ambulances continued to stream in to a field hospital nearby, its administrator said 10 fighters had been killed and 150 wounded.

Ahmed Mohammed Abu Oud also said that four ambulances had been destroyed by fire from Gaddafi forces, and two ambulance workers wounded.

There were no immediate casualty figures from the eastern side of the Mediterranean city, 360 kilometres (225 miles) east of Tripoli.

After a ferocious dawn barrage of artillery and rocket fire, hundreds of fighters tried to enter the city in columns of pick-up trucks mounted with anti-aircraft and machineguns.

Sustained NTC tank and mortar fire hit targets in the city, with much of it concentrated around the Ouagadougou centre, but the resistance was fierce and effective, NTC sources said.

Plumes of black smoke could be seen billowing up from several points in city, amid the sound of machinegun fire and explosions.

NATO planes flew overhead, but there were no reports of air strikes.

NTC fighter Barak Abu Hajar told AFP he had been in action earlier at the Ouagadougou centre and had brought out a wounded comrade.

"They're shooting from everywhere. RPGs and lots of bullets. We were told this was the final assault. Inshallah (God willing) we will take Sirte today."

Fighter Faisal Asker said, "We entered the Ouagadougou centre compound but fell back because of RPG and sniper fire. There's no cover there."

"We have orders to finish the mission today."

At the field hospital, just a couple of kilometres away from the Ouagadougou centre, the AFP reporter said ambulances with wailing sirens were arriving every couple of minutes.

A man with loud hailer, joined by others, shouted "Allahu akbar" (God is greatest) every time a patient was stretchered inside the derelict building housing the hospital.

A white minivan arrived and a crowd gathered round in prayer.

Inside there were four bodies wrapped in grey blankets, tied with white tape and a large white sticker giving their names.

The reporter saw five other dead, including the remains wrapped in a blanket of one person whose body medics said had been blown apart by shrapnel.

Earlier, officials at a field hospital 50 kilometres west of Sirte said 18 injured anti-Gaddafi fighters had been brought in, most of them with shrapnel wounds.

Another AFP correspondent said there were particularly violent clashes around and inside the university, near the city centre, and in the Mauritanian Quarter.

Sirte and Bani Walid, a desert town 170 kilometres (100 miles) southeast of of Tripoli, are Gaddafi's last major bastions against the NTC, which has ruled most of the oil-rich country since the veteran strongman was toppled in August.

As the fighting raged Thursday night, the fugitive Gaddafi called "on the Libyan people, men and women, to go out into the squares and the streets and in all the cities in their millions" to reject the NTC.

"I say to them, do not fear anyone. You are the people, you belong to this land," he said in a scratchy audio message broadcast on Syria-based Arrai television.

"Make your voice heard against NATO's collaborators," he said, in reference to the new regime.

Meanwhile, NTC reinforcements were on their way to Bani Walid for another assault of Gaddafi's loyalists who are fiercely defending the oasis town.

Mussa Ali Yunes, commander of the Jado Brigade, said "we are heading for the southern front of Bani Walid," speaking of a column of 1,000 men and hundreds of vehicles.

Yunes said efforts were being made to convince the remaining 10 percent of the population still there to leave before the new assault is launched after a month-long siege.

"The offensive could, possibly, be launched in two days, but that depends" on the situation, he added, explaining that the NTC forces were outgunned.

"There are many weapons in Bani Walid, weapons of high technology, very recent, coming from Russia," he said. "We need more precise weapons but also intelligence on the inside, particularly on the number of missiles they have.

"About 2,000 fighters are deployed on the northern front, but they only have light weapons for now, because all the heavy weapons are in Sirte."

Yunes said Gaddafi son "Seif al-Islam is in Bani Walid and possibly Gaddafi as well, but there is a 50 percent doubt about that. There are many Gaddafi loyalists in Bani Walid, more than in Sirte."