UPDATE: Al Jazeera reports that there's a lot of scepticism about this report.

So this is what "protecting civilians" looks like. Not so pretty, is it? Can you say "mission creep"?

BENGHAZI, Libya — The government of Col. Muammar el-Qaddafi said he survived an airstrike in Tripoli late Saturday night that killed one of his sons and three grandchildren, in the sharpest intensification yet of the NATO air campaign intended to pressure the Libyan leader from power.

The son, Seif al-Arab Muammar el-Qaddafi, 29, and the grandchildren, all said to be younger than 12, were possibly the first confirmed casualties in the airstrikes on the Libyan capital. And while the deaths could not be independently verified, the campaign against Libya’s most densely populated areas raised new questions about how broadly NATO is interpreting its United Nations mandate to protect civilians.

It is the second airstrike in seven days to hit a location intimately close to the Libyan leader, following a midnight attack last week that destroyed an office building in his compound where he and his aides sometimes work.

In a news conference early Sunday morning in Tripoli, a Qaddafi government spokesman called the strike an illegal attack. “This was a direct operation to assassinate the leader of this country,” said the spokesman, Musa Ibrahim. “This is not permitted by international law. It is not permitted by any moral code or principle.” He said that the colonel and his wife, who were staying at the house along with “friends and family,” were not hurt.

American and NATO officials have said they are not seeking to kill Colonel Qaddafi, and some have suggested it might not be very easy. But frustrated by the evasion and resilience of Colonel Qaddafi’s military, NATO has pledged to step up its strikes on the broader instruments of his power, including state television facilities and command centers in the capital.