U.N. Secretary-General Kofi Annan on Sunday repeated his call for an immediate halt to violence between Israel and Hezbollah, condemning an Israeli airstrike that killed at least 54 people and telling the U.N. Security Council he was "deeply disturbed" that his previous calls for cease-fire had gone unheeded.

Annan spoke at an emergency meeting of the council that he convened after the Israeli airstrike in Qana early Sunday. He said the council had a responsibility to demand an end to the violence.

"We meet at a moment of extreme gravity first and foremost fo the people of the Middle East but also for the authority of this organization and especially this council," Annan said. "Action is needed now before many more children, women and men become casualties of a conflict over which they have no control."

The council has so far been unable to take a stand on the fighting even though it has now continued for three weeks. That is partly because the United States, unlike other members of the council, has refused to back Annans calls for an immediate cease-fire.

In unusually frank terms, Annan said the council risked undermining its own authority if it does not take action. He said that was made clear by the attacks on U.N. headquarters in Beirut earlier Sunday.

"People have noticed its failure to act firmly and quickly during this crisis," Annan said.

Lebanese special envoy Nouhad Mahoud also criticized the council for its lack of action and said Israel was committing war crimes.

"Israel is committing atrocities against humanity," Mahoud said. "The fact that such massacres are yet ... to be taken up by resolutions of this august council — that fact does not mean that the truth is to remain hidden."