Tripoli - The youngest son of Muammar Gaddafi was killed in a NATO airstrike on a house where the Libyan leader and his family were staying at the time, a government spokesman said on Sunday.
The raid caused the deaths of Saif al-Arab Gaddafi, 29, the youngest son of Gaddafi, and three of Gaddafi's grandchildren, spokesman Mossa Ibrahim told a press conference.
The Libyan leader himself and his wife, who were in the house at the time, were in good health, while some other people were injured in the attack, Ibrahim said.
This was a direct attempt on the Libyan leader's life, a violation of international law which has no legal or political justifications, he said.
After the raid which took place around 8pm local time (1800 GMT) on Saturday, Ibrahim took a group of journalists to the site of the house located in a residential area in western Tripoli.
As a Xinhua correspondent witnessed at the scene, the three-storey building was partially destroyed, with part of the roofs completely caved in, leaving mangled rods of reinforcing steel hanging down among splintered chunks of concrete. The house was left empty with no dead bodies remaining there.
Libyan officials said the house was hit by three missiles. Two of them exploded, the third was seen lying in one of the rooms of the building.
After the airstrike, large numbers of Libyans took to the streets, protesting the NATO strikes against civilians and expressing their support and sympathy for Gaddafi and his family.
Meanwhile, NATO said it did stage airstrikes on Tripoli but would not confirm the Libyan claim about the deaths and the assassination attempt.
"NATO continued its precision strikes against Gaddafi regime military installations in Tripoli overnight, including striking a known command and control building in the Bab al-Azizya neighborhood shortly after 1800 GMT on Saturday evening," NATO said in a statement.
The alliance insisted all its targets are military in nature and linked to Gaddafi's "systematic attacks on the population."
The commander of the NATO operation, Lieutenant General Charles Bouchard, said he was aware of unconfirmed reports that some Gaddafi family members may have been killed and he regretted "all loss of life."
Asserting he would not leave, Gaddafi floated on Saturday a proposal for a cease-fire and negotiations in a televised speech and called on all parties to resort to dialogue only if NATO halts its airstrikes.
"Libya welcomes a cease-fire," Gaddafi said in his speech, adding that "a cease-fire cannot be done unilaterally."
However, Gaddafi made it clear that he will never leave his country and nobody can force him to leave.
"I don't have any function or post. If I were a president, my fate would be like the fates of the presidents of Tunisia and Egypt," Gaddafi said.
He said all parties concerned should follow the truce, and the NATO forces must stop their attacks.
Gaddafi ruled out the possibility that he will quit and leave Libya, which he has been ruling over the past 41 years.