Britain responded to the attack on its embassy complex, which left the buildings badly burned, by announcing that it was expelling the Libyan ambassador to London.
Nato's attack on a blast wall-ringed Gaddafi family compound in a residential area of Tripoli late on Saturday (local time) signalled escalating pressure on the Libyan leader who has tried to crush an armed rebellion that erupted in mid-February. Libyan officials denounced the strike as an assassination attempt and a violation of international law.
The Libyan government stepped up its shelling on the besieged western city of Misrata, pounding the port, which has been the rebel-held city's only lifeline. Heavy shelling also occurred elsewhere in the city throughout the day, killing 12 people and raising the two-day death toll to 29.
Gaddafi forces lobbed more than two dozen Grad rockets and mortars against the port in the evening, killing two people who were manning an improvised checkpoint outside the port. The volley of rockets also hit some aid that was deserted on the port's dock, causing a fire and filling the sky with smoke, said Ahmed al-Jamal, 27, who works at the port restaurant and was slightly injured.
"It was random fire but most of it hit near the port gate," said Abdel Hamid abou Zugeya, a medic with the Red Crescent who was there during the shelling.
Medics in Misrata said another 10 people were killed in other parts of the city and 29 were injured.
Misrata, which is the main rebel-held city in the west, has emerged as a key prize as the two sides have been locked in a stalemate with Gadhafi holding sway over the western half of the country and the rebels dominating the east.
Nato warplanes have been carrying out airstrikes in Libya for the past six weeks as part of a UN mandate to protect Libyan civilians.
The bombing that reportedly killed Gaddafi's son, Seif al-Arab, drew criticism from Russia, which cast doubt on Nato's assertion that the alliance is not targeting the Libyan leader or members of his family.
The 29-year-old had survived a 1986 US airstrike on his father's Bab al-Aziziya residential compound that killed his adopted sister - retaliation for the bombing attack on a German disco in which two US servicemen were killed. The US at the time blamed Libya for the disco blast.
"Statements by participants in the coalition that the strikes on Libya are not aimed at the physical destruction of ... Gaddafi and members of his family raise serious doubts," a Russian Foreign Ministry statement said.
It also said the "disproportionate use of force ... is leading to detrimental consequences and the death of innocent civilians." The ministry called for "an immediate cease-fire and the beginning of a political settlement process without preconditions."
Venezuelan President Hugo Chavez, a Gaddafi ally, also condemned the strike.
Nato acknowledged that it had struck a "command and control building," but insisted all its targets are military in nature and linked to Gaddafi's systematic attacks on the population.
"It was not targeted against any individual," Nato spokeswoman Carmen Romero said, adding the report of the deaths remained unconfirmed.
British Prime Minister David Cameron, without confirming fatalities, also told the British Broadcasting Corp that the strike was in line with the UN mandate to prevent "a loss of civilian life by targeting Gaddafi's war-making machine."
A Nato warplane bombed a residential complex taking up an entire block in Tripoli's Garghour neighbourhood, which is also home to several foreign embassies. The blast killed Gaddafi's second youngest son, Seif al-Arab, 29, when the Libyan leader and his wife, Safiya, were inside, said Libyan government spokesman Moussa Ibrahim. Three of Gaddafi's grandchildren, all younger than 12, were killed, but the Libyan leader was "in good health," he said. Ibrahim initially said Seif al-Arab was the youngest.
Bishop Giovanni Martinelli, the top Catholic clergyman in Tripoli, said he was shown several bodies in a hospital in the capital on Sunday. He said he was told that one of the bodies was that of Seif al-Arab Gaddafi, but that it was so badly disfigured that he could not make a positive identification.
"We saw the body. The body was completely disfigured," the bishop told The Associated Press.
He said he was told that among the bodies were those of the three children.
Footage broadcast on Libyan TV showed Martinelli and other clergymen speaking blessings in what appeared to be a morgue. Two of the bodies were covered by green Libyan flags, and a flower wreath leaned against a wall.
Neighbors said the complex bombed late on Saturday had served as the Gaddafi family home for years. It contained two residences, each with two bedrooms, as well as a den, a large communal space and a separate kitchen.
The kitchen clock, knocked from the wall, had stopped at 8:08 and 45 seconds, the time of the explosion. Cooking pots with leftover food, including stuffed peppers, noodles and a stew, had been covered with aluminum foil. In one of the living rooms, a pile of video games lay scattered on a sofa.
The bombing demolished the ceiling of the main single-storey building and tore a hole into the ground, displaying what looked like a basement. What appeared to be an unexploded rocket lay on the ground, which was covered by twisted metal and pieces of concrete. Hours after the blast, onlookers were permitted onto the grounds, some chanting pro-Gaddafi slogans.
In Rome, the Italian Foreign Ministry said its embassy and several others in Tripoli were damaged by vandals and accused the Gaddafi regime of failing to take measures to protect foreign missions. The ministry issued a statement on Sunday following reports from Tripoli that a fire had broken out at the Italian embassy. Italy withdrew its diplomats weeks ago.
A Foreign Office spokeswoman said the British embassy buildings, which include the ambassadors' residence, have been almost completely burnt down, with only the shells remaining. She said the buildings had been "ransacked, vandalized and completely destroyed," but they were empty at the time as all staff had already left.
British Foreign Secretary William Hague said the Libyan ambassador has been given 24 hours to leave the country. "I condemn the attacks on the British Embassy premises in Tripoli as well as the diplomatic missions of other countries," he said in a statement.
The United Nations pulled its 12 international staffers out of Tripoli and sent them to neighbouring Tunisia because of unrest in the Libyan capital, said Stephanie Bunker, spokeswoman for the UN Office for the Co-ordination of Humanitarian Affairs.
UN international staffers remain in the rebel stronghold of Benghazi, in eastern Libya.
Rebels celebrated the news of the airstrike that killed Gaddafi's son, although some questioned the veracity of the claim, saying the regime could be trying to discredit the international military campaign.
"We don't know if it is true or not because Gaddhafi is a liar. He is probably trying to put pressure on international community. I will only believe it if you put the body in front of me," said Khaled al-Urfi, a 34-year-old metalworker.
In addition to his eight biological children, Gaddafi also had an adopted daughter who was killed in the 1986 US airstrike.
Seif al-Arab is the second youngest of Gaddafi's seven sons and brother of the better known Seif al-Islam, who had been touted as a reformist before the uprising began. The younger Gaddafi had spent much of his time in Germany in recent years and was not involved in Libyan power structures as were many of his siblings.
The airstrike that killed Seif al-Arab came just hours after Gaddafi called for a mutual cease-fire and negotiations with Nato powers to end the bombing campaign. Nato rejected the offer, saying the alliance needed "to see not words but actions."
On Sunday morning, Gaddafi's troops shelled Misrata's port as a Maltese aid ship, the Mae Yemanja, unloaded food and medical supplies, said Ahmed al-Misrati, a truck driver helping move the cargo.
"We were still working this morning when they started firing rockets," said al-Misrati. "Some fell in the ocean, some on the pavement, some in the warehouses, and in the water in front of the boat."
The boat quickly embarked back to sea, he said.
Also on Sunday, several mortars hit Tunisian territory near the Libyan border crossing of Dhuheiba, the site of fierce fighting between pro-Gadhafi and rebel forces in recent days, said eyewitnesses. Fighting spilled into Tunisia on Friday as well.
An AP photographer witnessed a violent firefight on Sunday morning as Gaddafi loyalists tried to wrench the crossing from rebel control. Most of the mortars that hit Tunisian territory landed in uninhabited areas, except for two that impacted near a school
The mortars did not cause any casualties or significant damage, but they did scare the locals, said Mohamed Hedia, an area resident.
