PALESTINIAN president Mahmud Abbas today slammed as "a massacre" a deadly Israeli raid on a fleet of ships carrying aid to Gaza, in which at least 10 passengers were killed.

"We consider this to be a massacre and we condemn it," an official from Mr Abbas' office said on Palestinian television, announcing a three-day mourning period.

"We will have to take some difficult decisions this evening."

Arab League chief Amr Mussa slammed the attack as a "crime" against a humanitarian mission.

"We condemn this crime, taken against a humanitarian mission and people. They were trying to help people. They were not on a military mission. Everyone should condemn this," Mr Mussa said.

"We are now conducting calls to Arabs to decide on our next step," said Mr Mussa, who heads the 22-country organisation based in Cairo.

The Israeli army said "more than 10 people were killed" when navy seals stormed the boat, ending a high-profile mission by six ships to bring supplies to the blockaded Palestinian Gaza Strip.

According to Israel's private channel 10 television, Israeli marine commandos had opened fire after being attacked with axes and knives by a number of the passengers on board the aid ships, the television said, without giving the source of its information.

It was not clear whether the clashes took place on just one of the six boats making up the aid convoy.

