JERUSALEM: Israeli marines stormed aid ships bound for Gaza on Monday and at least 10 rights activists were killed, triggering a diplomatic crisis and an emergency session of the UN Security Council.

European nations, as well as the United Nations and Turkey, voiced shock and outrage at the bloody end to the international campaigners' bid to break Israel's blockade of the Gaza Strip.

The Israeli Navy stopped six ships ferrying 700 people and 10,000 tons of supplies toward the Palestinian enclave, but the unprecedented raid on ships in international waters and the massacre of unarmed civilians left Israel isolated and condemned.

Once-close Muslim ally Turkey said Israel has "lost all legitimacy". "A state that committed these crimes has lost all legitimacy in the international community," Turkish Foreign Minister Ahmet Davutoglu told the Security Council at an emergency session called to discuss the raid. "It is murder committed by a state. It has no justification whatsoever."

US President Barack Obama said he wanted the full facts soon and regretted the loss of life. Israeli Prime Minister Benjamin Netanyahu also voiced regret as he cut short a visit to Canada and rang Obama to call off a White House meeting planned for Tuesday. His White House meeting was intended to soothe ties with Obama, which have been strained by differences over Jewish settlement construction that had delayed a revival of peace talks with the Palestinians.

Palestinian President Mahmoud Abbas seemed unlikely to hold further sessions soon of US-mediated peace talks that began three weeks ago. He said: "What Israel has committed on board the Freedom Flotilla was a massacre."

As the captured foreign vessels were escorted into Israel's port of Ashdod, accounts were sketchy of the pre-dawn operation, some 120 km out in the Mediterranean. Black-clad commandos can be seen rappelling down from helicopters then pointing assault rifles, in some of the dramatic footage. Israel says the troops returned fire after they were attacked with live rounds, knives and clubs, but the organizers of the Gaza blockade busting bid insist the soldiers started shooting the moment they hit the deck.

"They fired directly into the crowd of civilians asleep," the Free Gaza Movement said.

Only selective footage of the confrontation has been broadcast as communications with the six ships participating in the flotilla appeared to have been scrambled during the operation.

Three choppers and several commando boats approached the flotilla at about 4 a.m. An Al Jazeera correspondent on board the Turkish ship "Mavi Marmara" said the Israeli soldiers continued shooting even though a white flag of surrender had been raised.

He said hundreds of Israeli troops attacked the ships and that the captain was among those wounded.

Indications are that most, if not all of those killed were aboard the Marmara, which carried the majority of the 700 activists who hoped to make their way toward the Gaza Strip.

Netanyahu said at least 10 activists died on the Mavi Marmara. Seven marines and 20 protesters were injured, the military said.

Protest organizers said they believed up to 16 people may have been killed, including six Turks. A senior Israeli officer said most of the dead were Turks. The convoy also featured Americans, Israelis, Palestinians and many Europeans.

Israel imposed a communications blackout on those aboard the convoy and other accounts of events were not available. Consular officials were at Ashdod seeking access to detained foreigners. Veteran Pakistani TV journalist Talat Hussain, who was on one of the boats covering the event, is missing, his family said.

Ambassadors from the 27 EU countries condemned Israel's use of violence against the flotilla of ships.

"The EU condemns the use of violence that has produced a high number of victims among the members of the flotilla and demands an immediate, full and impartial inquiry into the events and the circumstances surrounding it," the ambassadors said in a statement.

Earlier, France, Germany, Ireland, Britain, Spain and Greece whose citizens were on the boats expressed shock and outrage at the raid and the civilian deaths. Greece scrapped a series of joint military exercises that were planned with Israel.

In London, more than a thousand pro-Palestinian protesters demonstrated outside the Israeli Embassy in to denounce the killings.

Waving Palestinian flags and placards saying "Disarm Israel" and accusing Israel of "war crimes", the protesters had earlier marched through the capital and stopped outside the British prime minister's Downing Street residence.

The demonstrators, who were noisy but peaceful, then marched across London to gather near the Israeli Embassy which stands in a road blocked off by security gates which were guarded by hundreds of police.