NATO's attack on a Gadhafi family compound in a residential area of Tripoli late Saturday signaled escalating pressure on the Libyan leader who has tried to crush an armed rebellion that erupted in mid-February.
The alliance acknowledged that it had struck a "command and control building," but insisted all its targets are military in nature and linked to Gadhafi's systematic attacks on the population.
Libyan officials denounced the attack as a crime and violation of international law. However, British Prime Minister David Cameron, without confirming fatalities, told the British Broadcasting Corp. that the strike was in line with a U.N. mandate to prevent "a loss of civilian life by targeting Gadhafi's war-making machine."
The attack struck the house of one of Gadhafi's younger sons, Seif al-Arab, when the Libyan leader and his wife were inside, said Libyan government spokesman Moussa Ibrahim. Seif al-Arab, 29, and three of Gadhafi's grandchildren, all younger than 12, were killed, said Ibrahim.
Journalists taken to the walled complex of one-story buildings saw heavy bomb damage. The blast had torn down the ceiling of one building. Dust and smoke rose from the rubble, which included household items such as smashed toilet bowls, bathroom sinks and furniture among the broken walls and demolished floors. The mirror of a dressing table remained intact in the middle of a bedroom although the walls around it were demolished.
The bombing came hours after Gadhafi called for a cease-fire and negotiations in what rebels called a publicity stunt.
When news of the deadly strike spread, rebels honked horns and chanted "Allahu Akbar" or "God is great" while speeding through the western city of Misrata, which Gadhafi's forces have besieged and subjected to random shelling for two months, killing hundreds. Fireworks were set off in front of the central Hikma hospital, causing a brief panic that the light would draw fire from Gadhafi's forces.
On Sunday morning, Gadhafi's troops shelled Misrata's port as a Maltese aid ship, the Mae Yemanja, unloaded food and medical supplies, said Ahmed al-Misalati, a truck driver helping move the cargo.
"We were still working this morning when they started firing rockets," said al-Misalati. "Some fell in the ocean, some on the pavement, some in the warehouses, and in the water in front of the boat."
The driver said about a dozen rockets fired over 10 minutes struck three warehouses and a guard post. The boat quickly embarked back to sea, he said.
Last week, regime loyalists attempted to mine Misrata's harbor to close the besieged city's only link to the world.
NATO warplanes have been carrying out airstrikes in Libya for the past month as part of a U.N. mandate to protect Libyan civilians. Last week, British Defense Minister Liam Fox and U.S. Defense Secretary Robert Gates had told reporters at the Pentagon that NATO planes were not targeting Gadhafi specifically but would continue to attack his command centers.
The commander of the NATO operation, Canadian Lt. Gen. Charles Bouchard, said he was aware of unconfirmed reports that some Gadhafi family members may have been killed and he regretted "all loss of life, specially the innocent civilians being harmed as a result of the ongoing conflict."
Seif al-Arab Gadhafi, was one of the youngest of Gadhafi's seven sons and brother of the better known Seif al-Islam Gadhafi, who had been touted as a reformist before the uprising began in mid-February. The younger Gadhafi had spent much of his time in Germany in recent years.
Gadhafi's children had been increasingly engaged in covering up scandals fit for a soap opera, including negative publicity from extravagant displays of wealth such as a million-dollar private concert by pop diva Beyonce, according to a batch of diplomatic cables released by the secret-spilling WikiLeaks website.
But Seif al-Arab remained largely in the shadows, although he had a penchant for fast cars and partying when outside Libya.
Moammar Gadhafi and his wife were in Seif al-Arab's house in the capital's Garghour neighborhood when it was hit by at least one bomb dropped from a NATO warplane, according to Ibrahim.
Seif al-Arab "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.
The government spokesman said the airstrike was an attempt to "assassinate the leader of this country," which he said violated international law.
"The leader himself is in good health," Ibrahim said. "He was not harmed. The wife is also in good health," Ibrahim said, referring to Safiya Farkash, Gadhafi's second wife and a former nurse.
Ibrahim would not give the names of the three children killed, except to say they were nieces and nephews of Seif al-Arab and that they were younger than 12. He said the family is not releasing the names to protect its privacy.
Ibrahim said Seif al-Arab had been enrolled at a German university but had not yet completed his studies.
In addition to his eight biological children, Gadhafi also had an adopted daughter who was killed in a 1986 U.S. airstrike on his Bab al-Aziziya residential compound - retaliation for the bombing attack on a German disco in which two U.S. servicemen were killed. The U.S. at the time blamed Libya for the disco blast.
Venezuelan President Hugo Chavez, a Gadhafi ally, condemned Saturday's deadly strike, calling foreign military intervention in Libya "madness." He said he believes "they order they've given is to kill Gadhafi.
In Misrata, rebel fighters were rejoicing.
Standing outside an improvised triage unit in a tent in the parking lot, rebel fighter Abdel-Aziz Bilhaj, 22, welcomed the attack, saying it would make Gadhafi think twice about how he dealt with his people.
"It could make him more willing to back down on certain parts of his plan," Bilhaj said.
Medic Abdel-Moneim Ibsheir considered the strike a form of justice.
"Gadhafi was not far away, meaning he's not safe," he said as occasional explosions could be heard throughout the embattled city. "It's just like our children getting hit here. Now his children are getting hit there."
Eleven dead had reached the hospital morgue by midnight Saturday, including two brothers, ages 11 and 16. Two more had arrived by 1:30 a.m., and four more at another hospital.
In Tripoli, dozens danced, waved and clapped in unison at the Bab al-Aziziya compound early Sunday to show support for the regime. Heavy bursts of gunfire were heard in Tripoli after the attack.
The fatal airstrike came just hours after Gadhafi called for a mutual cease-fire and negotiations with NATO powers to end a six-week bombing campaign.
In a rambling pre-dawn speech Saturday, Gadhafi said "the door to peace is open."
"You are the aggressors. We will negotiate with you. Come, France, Italy, U.K., America, come to negotiate with us. Why are you attacking us?" he asked.
He also railed against foreign intervention, saying Libyans have the right to choose their own political system, but not under the threat of NATO bombings.
In Brussels, a NATO official said before Saturday's fatal strike that the alliance needed "to see not words but actions," and vowed the alliance would keep up the pressure until the U.N. Security Council mandate on Libya is fulfilled. NATO has promised to continue operations until all attacks and threats against civilians have ceased, all of Gadhafi's forces have returned to bases and full humanitarian access is granted.
Rebel leaders have said they will only lay down their arms and begin talks after Gadhafi and his sons step aside.
"The time for compromise has passed," said rebel spokesman Abdel-Hafidh Ghoga in a statement. "The people of Libya cannot possibly envisage or accept a future Libya in which Gadhafi's regime plays any role."
Associated Press writers Ben Hubbard in Misrata, Libya, Hadeel al-Shalchi in Cairo and Slobodan Lekic in Brussels contributed to this report.