The Libyan government have accused Nato forces of breaking international law with an attack said to have killed Colonel Muammar Gaddafi's youngest son.
Saif al-Arab Gaddafi, 29, died when his house was hit by at least one missile fired by a Nato warplane, according to spokesman Moussa Ibrahim.
Three of the dictators' grandchildren were also killed in the attack on the Tripoli house, he said.
Gaddafi and his wife were in the building, along with other friends and relatives, but were unharmed in the strike, Ibrahim said.
The spokesman said the attack was an clear attempt to kill the Libyan leader, and is against "any moral code or principle".
In a press conference, Ibrahim said: "This was a direct operation to assassinate the leader of this country. This is not permitted by international law. It is not permitted by any moral code or principle.
"If people claim they want to protect civilians we have again and again declared that we are ready for negotiation, ready for road maps for peace, ready for political transitional periods, ready for elections, ready for referendum.
"Nato does not care to test our promises. The West does not care to test our statements. They only care to rob us of our freedom, our wealth, which is oil, and our right to decide our future as Libyans."
Saif al-Arab Gaddafi was the sixth son of Gaddafi and brother of the better known Saif al-Islam Gaddafi.
The younger Gaddafi had spent much of his time in Germany in recent years and had studied at a German university.
He "was playing and talking with his father and mother and his nieces and nephews and other visitors when he was attacked for no crimes committed", Ibrahim said.
Journalists taken to the walled complex of one-storey buildings in a residential Tripoli neighbourhood saw heavy bomb damage.
The blast had torn down the ceiling of one building and left a huge pile of rubble and twisted metal on the ground.
On Tuesday, Defence Secretary Liam Fox and his US counterpart Robert Gates maintained that Nato planes were not targeting Gaddafi specifically but would continue to attack his command centres.
Nato said today its forces carried out precision strikes against Gaddafi regime military buildings in Tripoli, including a strike on "known command and control building" in the Bab al-Azizya neighbourhood.
But it did not verify media reports that members of Gaddafi's family had been killed.
Lieutenant-General Charles Bouchard, commander of Nato's Operation Unified Protector, said: "All Nato's targets are military in nature and have been clearly linked to the Gaddafi regime's systematic attacks on the Libyan population and populated areas. We do not target individuals."
Officials said the strike was part of Nato's strategy to disrupt the command and control of forces which have been attacking civilians.
Lt Gen Bouchard went on: "I am aware of unconfirmed media reports that some of Gaddafi's family members may have been killed.
"We regret all loss of life, especially the innocent civilians being harmed as a result of the ongoing conflict.
"Nato is fulfilling its UN mandate to stop and prevent attacks against civilians with precision and care - unlike Gaddafi's forces, which are causing so much suffering."
He added: "I want to remind again all civilians in Libya to distance themselves as much as possible from Gaddafi regime forces, equipment and known military infrastructure to reduce the potential danger to them."
Officials did not specify which nations were involved in the strike.Reuse content