Russia condemned a NATO airstrike in which a son and three grandchildren of Moammar Gaddafi were killed, saying Sunday the attack was a disproportionate use of force, the Associated Press reported.

The Foreign Ministry questioned NATO’s assertion that the alliance is not targeting Gaddafi or members of his family. A ministry statement also called for “an immediate cease-fire and political settlement,” AP said.

The youngest son of Gaddafi was killed in a NATO airstrike on his home Saturday evening, along with three of Gaddafi’s grandchildren, but the Libyan leader escaped unharmed, the Libyan government said Sunday.

Saif al-Arab Gaddafi, 29, was hosting a gathering of family and friends when three missiles struck his house just after 8 p.m., causing huge explosions that could be felt more than two miles away. The Libyan leader and his wife, Safiyah, were also there, government spokesman Moussa Ibrahim said, describing the attack as an assassination attempt.

A U.S. official said Saturday evening that U.S. intelligence agencies had not yet been able to confirm the report, while NATO said it had carried out a “precision strike” against “a known command and control building.”

In Brussels Sunday, NATO spokeswoman Carmen Romero said the Libyan government’s announcement that Gaddafi’s relatives were killed in the airstrike late Saturday remained unconfirmed, AP reported.

“We targeted a military command and control building with a precision strike,” Romero told the AP. “It was not targeted against any individual. It was a military target, clearly linked to the Gaddafi’s regime’s systematic attacks on the civilian population.”

A Russian lawmaker who often serves as a mouthpiece for the Kremlin’s views on foreign affairs was less diplomatic, according to the AP report.

“More and more facts indicate that the aim of the anti-Libyan coalition is the physical destruction of Gaddafi,” Konstantin Kosachyov, who heads the lower house of parliament’s international affairs committee, was quoted as saying.

Kosachyov called on Western leaders to make their position on the airstrikes clear.

“I am totally perplexed by the total silence from the presidents of the United States, France, the leaders of other Western countries,” Kosachyov said in an interview, according to the Interfax news agency. “We have the right to expect their immediate, comprehensive and objective assessment of the coalition’s actions.”

Russia abstained in the March vote in the U.N. Security Council that authorized the use of force in Libya to protect civilians.

Ibrahim said the attack was neither permitted under international law nor morally justifiable, and that it contravened NATO’s mandate under Security Resolution 1973 to protect Libyan civilians. Intelligence about Gaddafi’s whereabouts or plans must have been leaked to NATO, he said.

“We ask the world to look into this carefully, because what we have now is the law of the jungle,” he said. “How is this helping in the protection of civilians?’’

Hours earlier, Gaddafi had called for a cease-fire and negotiations with NATO but refused to surrender power. Even as he spoke, alliance warplanes struck a government complex in the capital.

Ibrahim said NATO’s response was proof that it was not interested in peace or in protecting civilians. “We renew our call for peace and negotiations,” he said.

Reporters were taken to the house in Tripoli’s upscale Gharghour neighborhood. One building had been turned into a wreck of shattered concrete and twisted metal, with an unexploded missile lying in the rubble, and a huge crater that had unearthed what looked like an underground cellar or bunker.

The walls of an adjacent building were partly destroyed. In one room, a television was still turned on, and a pile of PlayStation games lay on a sofa, including Modern Warfare 2 and Fifa Soccer 10. A pair of Homer Simpson slippers was half buried in the dust.

Ibrahim did not identify the children who were killed but said they were all younger than 12.

In another building, there were smears of blood on a shattered mirror on the floor of a room that looked like a den, with a large flat-screen television on one wall and a bar in a corner. A children’s book was also on the ground.

NATO said the strike was part of its strategy to disrupt the Libyan government’s command and control systems. “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,” said Lt. Gen. Charles Bouchard, commander of NATO’s Operation Unified Protector.

“I am aware of unconfirmed media reports that some of Gaddafi’s family members may have been killed,” he said. “We regret all loss of life, especially the innocent civilians being harmed as a result of the ongoing conflict. NATO is fulfilling its U.N. mandate to stop and prevent attacks against civilians with precision and care — unlike Gaddafi’s forces, which are causing so much suffering.”

Saif al-Arab, not to be confused with his higher-profile elder brother Saif al-Islam, had yet to complete his studies in Germany. He had kept a lower profile than most of his brothers but was briefly in the spotlight in 1996 when he brawled with a nightclub bouncer in Munich.

In Tripoli, Gaddafi supporters took to the streets, waved the green flags of the regime and fired guns in the air. The crowd swelled at Bab al-Aziziyah, Gaddafi’s compound, where hundreds of people gather every night to express their support for their leader and offer themselves as human shields.

Guns were also fired in the air in the eastern city of Benghazi, the de facto capital of the opposition, but in celebration rather than in defiance. Young men took to the streets, waving their arms in the air and displaying the flag of the opposition, the skies alight with tracer fire. They also honked car horns and screamed “victory is ours,” passing under streetlights with effigies of Gaddafi hanging from the posts.

“Now Moammar Gaddafi knows what it's like to lose a son, the way he has killed our sons and our people,” said Msalem Iqmati, 25, a pharmacist. He flashed victory signs to cars speeding by. At least 10 of Iqmati’s relatives and friends have been killed since the Libyan revolution began Feb. 17.

A rebel spokesman said he knew that Gaddafi would use the deaths to paint the NATO operation as a mission to kill him rather than save civilians. Thousands of Libyans have been killed since the revolt began and eventually turned into an imbalanced war between a ragtag team of novice fighters with the opposition and a well-armed force from Gaddafi.

“He’ll milk it for all he can,” said Jalal el Gallal, a rebel spokesman in Benghazi. “Now he knows how the Libyans feel and it’s a shame they didn’t get [Gaddafi]. . . . We need this to be over and done with and, frankly speaking, this is the easiest way.”

NATO has been consistently criticized for not doing enough to protect civilians, and with people still being killed by government shelling every day in Misurata, Gallal chose not to celebrate on Sunday morning. “We’ll celebrate when [Gaddafi] is gone,” he said.

The announcement brought back memories of the U.S. airstrike in Tripoli in 1986 that killed a baby named Hanna. Gaddafi claimed she was his adopted daughter, but many believe he adopted her posthumously to solicit global sympathy. Some revelers in the east on Sunday wondered whether the news of Saif al-Arab’s death, the least well known of Gaddafi’s eight children, was another stunt by Libya’s erratic leader.

The U.N. resolution that authorized the military campaign against the Gaddafi government does not specifically permit strikes intended to kill the Libyan leader or members of his inner circle. While NATO bombs have repeatedly hit government facilities in the Libyan capital, including office buildings used by Gaddafi, NATO and U.S. officials have said the intended targets were command-and-control facilities, and not the Libyan leader or his sons.

But U.S. and European officials have acknowledged seeking to increase pressure on top Libyan leaders in hopes of encouraging defections or perhaps even persuading Gaddafi to step down. U.S. congressional leaders in recent days have urged NATO to be more aggressive, and some have urged the alliance to target Gaddafi himself.

“I can’t think of anything that would protect the civilian population of Libya more than the removal of Moammar Gaddafi,” Sen. Joseph I. Lieberman (I-Conn.) told CNN’s “State of the Union” on April 24.

A week ago, NATO jets launched two guided bombs into the Bab al-Aziziyah complex in Libya, part residence for Gaddafi, part government offices and part military base. No one was seriously hurt.

The White House denied that the strike was intended to kill Gaddafi and said it was not coalition policy to “decapitate, if you will, or to effect regime change in Libya by force.”

Earlier Saturday, in a rambling address on state television that lasted 80 minutes, Gaddafi appeared both calm and defiant, if slightly subdued, describing NATO’s military intervention as a “massacre.”

In Brussels, a NATO official rejected the cease-fire offer, telling the Associated Press that the alliance needed “to see not words, but actions,” and that NATO would keep up the pressure until the U.N. Security Council mandate to protect Libyan civilians was fulfilled. Rebels also rejected Gaddafi’s offer of a cease-fire as “lies.”

Gaddafi, who has ruled for more than four decades, said he would negotiate and observe a cease-fire if NATO “stopped its planes.” But even as he made the offer, he appeared to dismiss that possibility, describing his enemies as al-Qaeda operatives who do not understand what a truce means.

He also refused to step down or leave the country as the rebels — and the United States, Britain and France — demand.

“I'm not leaving my country,” Gaddafi said. “No one can force me to leave my country, and no one can tell me not to fight for my country.”

Western officials say Gaddafi needs to offer more than just a cease-fire, including withdrawing his forces from cities such as Misurata, for a political settlement to proceed.

Government forces continued to shell Misurata on Saturday. At least 16 people were killed in the attacks, doctors in Hikma Hospital said via Skype. More than 400 people have been killed in attacks, many civilians, in the two-month siege of the third-largest city in Libya. More than 1,000 are presumed dead, doctors there say.

“The injured are unknown; they’re still bringing in these poor people, sleeping in their homes,’’ Khaled al-Falgha said, a doctor, said. He added that he was “very happy’’ about Saif al-Arab’s death, saying that “NATO just needs to continue.”

Fadel reported from Benghazi. Staff writers Joby Warrick and Mary Beth Sheridan in Washington contributed to this report.