Sirte: Muammar Gaddafi's besieged hometown of Sirte was rocked by heavy Street fighting on Friday, as the ex-leader called on Libyans to turn out in their millions to demonstrate against the country's new rulers.

A news agency said there were particularly violent clashes around and inside the university, near the city centre.

Street fighting and heavy bombardment also continued from overnight at the Ouagadougou conference centre, a major stronghold of pro-Gaddafi forces, while the Mauritanian Quarter was also under attack.

Meanwhile, medics 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, but that there were no immediate reports of any killed.

Gaddafi made his call on Thursday on a television channel, as the National Transitional Council's forces pressed their three-week campaign to capture Sirte.

"I call 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, the deposed leader said in a scratchy audio message.

"I say to them, do not fear anyone. You are the people, you belong to this land," said Gaddafi, whose whereabouts are unknown but is widely thought to still be in Libya.

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