Updated

After two airstrikes in a week on targets close to Moammar Gadhafi, NATO was on the defensive Sunday over accusations that it was overstepping its mandate by trying to kill the Libyan leader.

Russia said Sunday that the bombing of the home of Gadhafi's youngest son raised "serious doubts" about NATO's assertions that it is not targeting the Libyan strongman or his relatives.

"Disproportionate use of force ... is leading to detrimental consequences and the death of innocent civilians," the Russian Foreign Ministry warned.

International law does not explicitly forbid attacks on military commanders during wartime, but the U.N. Security Council mandate authorizing NATO action charged alliance forces with establishing a no-fly zone and protecting civilians from attack.

Security council members Russia, China and Brazil have warned that attempts to change the regime or eliminate its members would be a violation of the mandate.

Alliance officials and allied leaders emphatically denied they were hunting Gadhafi in order to break a stalemate in the war between the better-trained government forces and the lightly armed rebels. NATO said the Libyan government's announcement that Gadhafi's son and three grandchildren were killed in the airstrike late Saturday remained unconfirmed.

"All NATO's targets are military in nature and have been clearly linked to the Gadhafi regime's systematic attacks on the Libyan population and populated areas. We do not target individuals," said Canadian Lt. Gen. Charles Bouchard, who commands NATO's operation in Libya.

Bouchard said the strike was part of NATO's strategy to disrupt and destroy "the command and control of those forces which have been attacking civilians."

Michael Clarke, director of the Royal United Services Institute, a London military think tank, noted that NATO warplanes have been shifting their focus in the past two weeks, from providing close support for the rebels on the front lines to focusing on military and government communication nodes. The immediate aim appeared to be to impair Gadhafi's ability to direct units surrounding the besieged enclave of Misrata on the Mediterranean coast, where pro-regime forces have suffered a series of setbacks, he said.

Another aim could be to increase the psychological pressure on Gadhafi and the people close to him, by demonstrating "that the war is getting closer to them," he said.

Another analyst said that there was a fine line between hitting military command-and-control centers, and hitting the people commanding and controlling Libya's armed forces.

"You're obviously risking hitting Gadhafi and members of his family, certainly those members involved in commanding the military," said Nate Hughes, director of military analysis at Stratfor, a global intelligence company.

Hughes said there was confusion about the aim of the strikes partly because of an "inherent contradiction" about what NATO's military objectives were. Politicians in the U.S., Britain and the Netherlands are talking about forcing Gadhafi out of power but NATO continues to insist that the strongman is not a target, he noted.

NATO took over command of the operation on March 31, after its governing body approved military plans to implement a U.N. Security Council resolution calling for the protection of civilians from attacks by regime troops.

One of the first targets of the international force after the start of hostilities, was Gadhafi's Bab al-Aziziya presidential compound — which was previously bombed by U.S. warplanes in 1986 in retaliation for the attack on a German disco in which two U.S. servicemen were killed.

Last Monday, another strike on the same complex destroyed two more buildings.

At a joint news conference a day later, U.S. Defense Secretary Robert Gates and British Defense Minister Liam Fox denied the warplanes had targeted Gadhafi specifically, but said they would continue to take aim at his command centers.

NATO says the air offensive, which began on March 21 with attacks by a U.S.-led coalition, has so far destroyed or damaged about 600 targets, including about 200 tanks and armored personnel carriers, as well as dozens of surface-to-air missile sites, ammunition dumps and artillery pieces.

It declined to say Sunday how many command centers had been attacked.

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Lynn Berry in Moscow contributed.