Libyan dictator's Muammar Gaddafi's youngest son and three grandchildren aged below 12 were killed in a NATO air strike, and the dictator himself barely survived.

The strike marked an escalation of international efforts to prevent the Libyan regime from regaining momentum, the Washington Post points out. It comes after on Saturday Gaddafi offered a bilateral ceasefire, while the severe fighting between the Gaddafi loyalist forces and the rebels in the besieged city of Misrata is continuing.

The attack struck the house of Gadhafi's youngest son, Seif al-Arab, when the Libyan dictator and his wife were inside. White House spokesman Shin Inouye declined to comment on the developments in Libya, referring questions to NATO.

The alliance acknowledged that it had struck a "command and control building in the Bab al-Azizya neighborhood" Saturday evening, but it could not confirm the death of Gaddafi's son and insisted all its targets are military in nature and linked to Gadhafi's systematic attacks on the population.

The commander of the NATO operation, Canadian Lt. Gen. Charles Bouchard, said he was aware of unconfirmed reports that some Gaddafi 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 Gaddafi, 29, was the youngest son of Gaddafi and brother of the better known Seif al-Islam Gaddafi, who had been touted as a reformist before the uprising began in mid-February. The younger Gaddafi had spent much of his time in Germany in recent years.

Moammar Gadhafi and his wife were in the Tripoli house of his 29-year-old son when it was hit by at least one bomb dropped from a NATO warplane, according to Libyan spokesman Moussa Ibrahim.

"The leader himself is in good health. He was not harmed. The wife is also in good health," the spokesman said as cited by the Washington Post.