Government spokesman Mussa Ibrahim accused the Western alliance of “deliberately targeting civilians,” insisting there were no military targets anywhere near the residential neighbourhood of the capital that was hit.

Nato said it was looking into the Libyan claim.

Ibrahim demanded that the alliance end its “aggression” to pave the way for dialogue, speaking just hours after organisations including the the Arab League, the European Union and the United Nations highlighted the importance of “accelerating the launch of a political process” to end the conflict.

Journalists were taken to the al-Arada district of Tripoli before 1 am to see rescue teams helped by bystanders desperately searching for survivors among the wreckage of a two-storey block of flats.

An AFP correspondent saw two bodies pulled from the rubble.

Journalists were then taken to a Tripoli hospital where they were shown the bodies of a woman and two toddlers that officials said were members of the same family and had died in the raid.

Ibrahim said that four passers-by were also killed, bringing the death toll to nine, and that 18 people were wounded.

A Nato official in Brussels confirmed that the alliance had planes in the air over Tripoli over the past 24 hours.

“We're aware of the claim made by the Libyan regime and we're looking into it,” a second Nato official told AFP.

If confirmed, the civilian deaths would be an embarrassment for the alliance which has been leading the bombing campaign under a UN mandate to protect civilians.

“It is another night of massacre, terror and horror at the hands of Nato,” the Libyan government spokesman charged.

Western leaders “are morally and legally responsible for these murders,” Ibrahim said.

“This is not propaganda. It is not something that we can stage.” Libyan officials have been on the defensive over their credibility after they showed journalists a little girl being treated in hospital two weeks ago and said she had been wounded in a Nato air strike. A member of the medical staff said she had been injured in a traffic accident.

Ibrahim called on Nato to halt its “aggression” against Libya to pave the way for dialogue to end a conflict now in its fifth month.

“Nato is very good at attacking and killing people but it is very bad at starting dialogue,” he said.

The alliance has acknowledged mis-hits in the past, most of them involving rebel fighters wrongly identified as loyalist troops.

Only Saturday, Nato acknowleged that aircraft under its command had accidentally hit a rebel column near the oil refinery town of Brega on the frontline between the rebel-held east and the mainly government-held west on Thursday.

“Nato can now confirm that the vehicles hit were part of an opposition patrol,” it said in a statement.

“This incident occurred in an area of conflict between Qadhafi forces and opposition forces.

“We regret any possible loss of life or injuries caused by this unfortunate incident,” Nato said.