Palestinian members of the Hamas naval police and civilian defense officers ride a boat at Gaza port during a display of their preparations ahead of the expected arrival of a flotilla of hundreds of pro-Palestinian activists trying to sail into the Gaza Strip, in Gaza city, Friday, May 28

Pro-Palestinian activists demonstrate a day before the expected arrival of a flotilla of hundreds of pro-Palestinian activists carrying 10,000 tons of supplies into the Gaza Strip, in Paris, Friday May 28, 2010

Israeli Navy sailors embark on a warship in order to stop a flotilla of activists attempting to deliver aid to Gaza in spite of Israel's blockade May 30, 2010 in Haifa, Israel

Israeli Navy sailors embark on the I.N.S. Hanit in order to stop a flotilla of activists attempting to deliver aid to Gaza in spite of Israel's blockade May 30, 2010 in Haifa, Israel

Palestinians ride boats in Gaza waters as a flotilla of aid ships leaves for the blockaded territory (AP)

Palestinian Islamic Jihad supporters hold Turkish flags as they ride on their motorcycles during a protest in Gaza City, Monday, May 31, 2010.

This video image released by the Turkish Aid group IHH Monday May 31, 2010 purports to show Israeli soldiers aiming a gun on the deck of a Turkish ship, part of an aid convoy heading to the Gaza Strip

Image released by the Turkish Aid group IHH Monday May 31, 2010 purports to show Israeli soldiers aboard a military vessel in international waters off the Gaza

This video image released by the Turkish Aid group IHH Monday May 31, 2010 purports to show an injured passenger on a Turkish ship, part of an aid convoy heading to the Gaza Strip

Israeli Navy soldiers prepare to disembark a missile ship as the Israeli Navy intercepts peace boats bound for Gaza on May 31, 2010

Israeli Navy soldiers aboard a boat as the Israeli Navy intercepts peace boats bound for Gaza on May 31, 2010

Israelis attend a demonstration in support of Israel following a deadly raid by the Israel military on an aid flotilla bound for the blockaded Gaza

An Hasidic Jew, a group who traditionally do not agree with Israel's action against Palestine, reads scripture during a campaign in Whitehall, London

A large crowd of protesters stand at the entrance to Kensington Palace Green and the Israeli Embassy

Some of the several hundred people in Derry's Guild Hall Square in protest at the raid on the aid flotilla which was travelling to Gaza

Deputy First Minister Minister Martin McGuinness who joined several hundred people in Derry's Guild Hall Square in protest at the raid on the aid flotilla which was travelling to Gaza

Israeli commandos today stormed six ships carrying hundreds of pro-Palestinian activists on an aid mission to the blockaded Gaza Strip, killing at least 19 people and wounding dozens more.

Israel said a total of five soldiers were wounded, two seriously, including at least one hit by live fire. Two of the dead activists had fired at soldiers with pistols, the army said.

"On board the ship we found weapons prepared in advance and used against our forces," declared Israel's deputy foreign minister, Danny Ayalon.

"The organisers' intent was violent, their method was violent and the results were unfortunately violent. Israel regrets any loss of life and did everything to avoid this outcome."

However the tough Israeli response drew condemnations from Turkey, France and the UN's Mideast envoy, while Greece suspended a military exercise with Israel and postponed a visit by Israel's air force chief.

About 10,000 Turks also marched from Israel's Consulate in Istanbul toward the city's main square, shouting slogans denouncing Israel. The protesters had earlier tried storm the Consulate building but were blocked by police.

The Israeli ambassadors in Sweden, Spain, Denmark and Greece were summoned for meetings, and the French foreign minister called for an investigation.

In neighbouring Jordan, hundreds demonstrated in the capital Amman to protest the Israeli action and demand that their government breaks diplomatic relations with the Jewish state.

Israeli security forces were on alert across the country. Palestinian President Mahmoud Abbas condemned the Israeli "aggression," declared three days of mourning across the West Bank and called on the UN Security Council and Arab League to hold emergency sessions on the incident.

The United Nations expressed "shock" and condemned the killings. "We are in contact with the Israeli authorities to express our deep concern and to seek a full explanation," said a statement from the highest-ranking UN official in the region, Robert Serry.

A reporter on one of the boats said the Israelis fired at the vessel before boarding it, but the Israelis claimed they only opened fire after being attacked by activists with sticks, knives and live fire.

The activists were headed to Gaza on a mission designed to draw attention to a three-year-old Israeli blockade of the coastal territory. Israel imposed the blockade after Hamas militants took power there.

"It's disgusting that they have come on board and attacked civilians. We are civilians," said Greta Berlin, a spokeswoman for the Free Gaza movement, which organised the flotilla.

Speaking from the east Mediterranean island of Cyprus, she said she had lost contact with the flotilla in the early hours.

Israel had declared it would not allow the ships to reach Gaza and had offered to transfer the aid to Gaza from an Israeli port. Israeli naval commandos raided the ships while they were in international waters after ordering them to stop about 80 miles from Gaza's coast, according to a pro-Palestinian activist in Greece involved in the aid mission.

A Turkish website showed video of pandemonium on board one of the ships, with activists in orange life jackets running around as some tried to help an activist apparently unconscious on the deck. The site also showed video of an Israeli helicopter flying overhead and Israeli warships nearby.

Turkey's NTV showed activists beating one Israeli soldier with sticks as he rappelled from a helicopter onto one of the boats.

The al-Jazeera satellite channel reported from the Turkish ship leading the flotilla that Israeli navy forces fired at the ship and boarded it, wounding the captain.

The Israeli military said troops only opened fire after encountering unexpected resistance from the activists. Activists attacked troops with knives and iron rods, and one activist wrested a serviceman's weapon.

A total of four soldiers were wounded, including at least one hit by live fire, the army said. Two of the dead activists had fired at soldiers with pistols, the army said.

"They planned this attack," said Israeli military spokeswoman Lt. Col. Avital Leibovitch. "Our soldiers were injured from these knives and sharp metal objects ... as well as from live fire."

The ships were being towed to the Israeli port of Ashdod, and the wounded were evacuated by helicopter to Israeli hospitals, officials said.

There were no details on the identities of the casualties, or on the conditions of some of the more prominent people on board, including 1976 Nobel Peace Prize laureate Mairead Corrigan Maguire of Northern Ireland, European legislators and Holocaust survivor Hedy Epstein, 85.

The Free Gaza Movement is an international group of pro-Palestinian activists that claims the blockade, imposed three years ago after the militant Islamic Hamas group overran Gaza, is unjust and a violation of international law.

Organisers included people affiliated with the International Solidarity Movement, a pro-Palestinian group that often sends international activists into battle zones, and the IHH, a Turkish aid group that Israel accuses of having terrorist links.

News of the attack sparked violent protests in Turkey, which had unofficially supported the aid mission and has been vocally critical of Israeli military operations against Palestinians in Gaza.

Police blocked dozens of stone-throwing protesters who tried to storm the Israeli consulate in Istanbul.

The Turkish Foreign Ministry condemned the Israeli raid and said it was summoning the Israeli ambassador for an "urgent explanation". It says Israel violated international law and will suffer consequences.

The flotilla of three cargo ships and three passenger ships carrying 10,000 tons of aid and 700 activists was carrying items that Israel bars from reaching Gaza, like cement and other building materials. The activists said they also were carrying hundreds of electric-powered wheelchairs, prefabricated homes and water purifiers to the territory's 1.5 million residents.

"We did not want to see confrontation," said Mark Regev, a spokesman for Israeli Prime Minister Benjamin Netanyahu, who is in Canada.

"We made repeated offers to the boats that they come to the (Israeli) port of Ashdod unload the humanitarian cargo, and we guaranteed to pass all humanitarian items through the crossings to the Gaza Strip. Unfortunately, they rejected our offers and chose the path of confrontation."

The head of the Gaza Hamas government, Ismail Haniyeh, condemned the "brutal" Israeli attack.

"We call on the secretary-general of the UN, Ban Ki-moon, to shoulder his responsibilities to protect the safety of the solidarity groups who were on board these ships and to secure their way to Gaza," Haniyeh said.

The flotilla began the journey from international waters off the coast of Cyprus on yesterday afternoon after two days of delays.

After nightfall, three Israeli navy missile boats left their base in Haifa, steaming out to sea to confront the ships. Two hours later, Israel Radio broadcast a recording of one of the missile boats warning the flotilla not to approach Gaza.

"If you ignore this order and enter the blockaded area, the Israeli navy will be forced to take all the necessary measures in order to enforce this blockade," the radio message continued.

This is the ninth time that the Free Gaza movement has tried to ship in humanitarian aid to Gaza since August 2008.

Belfast Telegraph