Libya will be a modern, democratic state founded on "moderate Islam", Mustafa Abdul-Jalil, the prime minister of Libya's interim National Transitional Council, has told a cheering crowd in Tripoli.

Joined in Martyr's Square by several dozen revolutionary leaders, and backed by a firework display, Jalil told the thousands of flag-waving supporters that Libya would not be a secular state.

Jalil said: "We strive for a state of the law, for a state of prosperity, for a state that will have Islamic sharia law the basis of legislation."

"We are a Muslim nation, with a moderate Islam, and we will maintain that. You are with us and support us - you are our weapon against whoever tries to hijack the revolution."

Urging the crowd not to take retribution against political opponents, Jalil said that "moderate" Libyans should accept their differences without resorting to fighting.

"Absolutely, there will be tensions. There will be different views. That's the whole point of the revolution ... The main thing now is how to solve these conflicts in a peaceful way, not resort to armed fighting."

Jalil's words come after Anders Fogh Rasmussen, the secretary-general of Nato, told The Daily Telegraph in an interview that Islamic extremists would "try to exploit" the country's weaknesses in the wake of the revolution.

It also came as Amnesty International published a report calling on the interim rulers to break with the abuses of the past.

“The new authorities must make a complete break with the abuses of the past four decades and set new standards by putting human rights at the centre of their agenda," Amnesty International's senior director Claudio Cordone said.

"The onus now is on the NTC to do things differently, end abuses and initiate the human rights reforms that are urgently needed."

Meanwhile fighters loyal to Muammar Gaddafi attacked killed up to 15 opposition fighters in Ras Lanuf, a key oil-producing town in the east of the country, as the former leader called for further resistance in a statement.

"All that remains for us is the struggle until victory and the defeat of the coup," Gaddafi was reported to have said in the message, which was meant to have been televised but was held back by Syrian-based broadcasters citing security concerns.

"It was meant to show the leader among his fighters and people, leading the struggle from Libyan lands," said Mishan Jabouri, owner of the Arrai channel who decided not to broadcast the video.

Fighting in the towns of Sirte and Bani Walid which are still held by the rebels, has continued to be more fierce than expected.

Elsewhere, officials in Niger have confirmed that 32 Libyans, including Gaddafi's son Saadi and three military leaders, had arrived in the country in the past ten days.

"We have confirmed with the government of Niger that Saadi crossed over [and] that they are either in the process or have already brought him to the capital of Naimey and intend to detain him," US State Department spokeswoman Victoria Nuland told Reuters on Monday.

China, the last member of the UN Security Council to have held back from recognising the NTC, has now accepted the interim government's new authority.

The state-run Xinhua news agency reported on Monday that Beijing: "officially recognised the ... NTC of Libya as the ruling authority and representative of the Libyan people.