A NATO air strike on a residential building in Tripoli has killed Saif-al Arab Qadhafi, the youngest son of their leader Muammar Qadhafi, and three grandchildren, Libyan authorities have claimed.

If confirmed, Saturday night's NATO attack will mark a serious escalation in the western military alliance's air campaign in Libya. Analysts say that by going after regime figures, as appears to be the case, NATO could be legitimately challenged for violating the United Nations Security Council mandate, which has been specific in permitting air strikes, only for the protection of Libyan civilians. Mr. Saif-al-Arab, 29, a student in Germany was among the least known of Col. Qadhafi's seven sons.

Libya's official spokesman, Moussa Ibrahim said the deadly missile strike was an assassination attempt on Col. Qadhafi's life. The leader was inside the building with his wife at the time of the attack.

Contradicting the Libyan government's assertion, NATO said it had carried out a “precision strike” against “a known command and control building.”

The alliance's version has already been challenged by Russia, which, along with China and India, had abstained during the United Nations vote on Libya that had been strongly supported by France, Britain and the United States. On Sunday, the Russian Foreign Ministry asserted that the statements by NATO members that “airstrikes against Libya are not aimed at physically destroying Muammar Qadhafi and members of his family cause serious doubts.”

The Libyan opposition, headquartered in Benghazi, expressed disappointment that Saturday's missile strikes in Tripoli failed to assassinate Mr. Qadhafi.

More In: International | News