JERUSALEM – Israel's defense minister has expressed regret for the deaths of pro-Palestinian activists in a clash with navy commandos. But he has blamed the violence on organizers of a flotilla carrying aid to the blockaded Gaza Strip. Speaking at a Monday news conference in Tel Aviv, Ehud Barak called the aid flotilla a "political provocation" by anti-Israel forces. He said the sponsors of the flotilla are violent. Israel's military chief, Lt. Gen. Gabi Ashkenazi, said soldiers were forced by violent activists to respond with live fire. At least 10 activists were killed in Monday morning's clash in international waters of Israel's Mediterranean coast. THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below. JERUSALEM (AP) — Israeli commandos on Monday stormed six ships carrying hundreds of pro-Palestinian activists on an aid mission to the blockaded Gaza Strip, killing at least 10 people and wounding dozens after encountering unexpected resistance as the forces boarded the vessels. The operation in international waters off the Gaza coast was a nightmare scenario for Israel that looked certain to further damage its international standing, strain already tense relations with Turkey — the unofficial sponsor of the mission — and draw unwanted attention to Gaza's plight. The tough Israeli response drew condemnations from Turkey, France and the U.N.'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 earlier Monday tried storm the Consulate building but were blocked by police. In response, Israel advised its citizens Monday to avoid travel to Turkey and instructed those already there to keep a low profile and avoid crowded downtown areas. The Israeli ambassadors in Sweden, Spain, Denmark and Greece were summoned for meetings, and the French foreign minister called for an investigation. Activists from all of those European countries were on board the flotilla. In neighboring Jordan, hundreds demonstrated in the capital Amman to protest the Israeli action and demand that their government breaks diplomatic relations with the Jewish state. There were conflicting accounts of what happened early Monday. An Al-Jazeera reporter on one of the Turkish ships said the Israelis fired at the vessel before boarding it. The Israelis, who had declared they would not let the ships reach Gaza, said they only opened fire after being attacked by activists with sticks, knives and live fire from weapons seized from the Israeli commandos. "On board the ship we found weapons prepared in advance and used against our forces," declared Israel's deputy foreign minister, Danny Ayalon. "The organizers' 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." 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 U.N. Security Council and Arab League to hold emergency sessions on the incident. Ismail Haniyeh, leader of the rival Hamas government in Gaza, condemned the "brutal" Israeli attack and called on U.N. Secretary-General Ban Ki-moon to intervene. The activists were headed to Gaza on a mission meant to draw attention to a 3-year-old Israeli blockade of the coastal territory. Israel imposed the blockade after Hamas, which it considers a terrorist group, violently seized the territory. Critics say the blockade has unfairly hurt Gaza's 1.5 million people. "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 organized the flotilla. She spoke from the Mediterranean island of Cyprus and said she had lost contact with the flotilla. Before the ships set sail from waters off the east Mediterranean island of Cyprus on Sunday, Israel had urged the flotilla not to try to breach the blockade and offered to transfer the cargo to Gaza from an Israeli port, following a security inspection. Israeli naval commandos stormed the ships in a predawn raid while they were in international waters after ordering them to stop about 80 miles (130 kilometers) from Gaza's coast, according to activists. 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 by telephone from the Turkish ship leading the flotilla that Israeli navy forces fired at the ship and boarded it, wounding the captain. "These savages are killing people here, please help," a Turkish television reporter said. The broadcast ended with a voice shouting in Hebrew, "Everybody shut up!" The Israeli military said troops only opened fire after encountering unexpected resistance from the activists. Activists attacked troops with knives and iron rods, and opened fire with two pistols seized from the forces. A total of five soldiers were wounded, two seriously, 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 violent takeover threatened to deal yet another blow to Israel's international image, already tarnished by war crimes accusations in Gaza and its blockade of the impoverished Palestinian territory. It occurred a day before Prime Minister Benjamin Netanyahu was to meet with President Barack Obama at the White House to discuss the Middle East peace process. The ships were being towed to the Israeli port of Ashdod, and wounded were evacuated by helicopter to Israeli hospitals, officials said. One of the ships had reached port by midday. 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. Satellite phones on board the ships were turned off, and communication with a small group of reporters embedded with the Israeli military was blocked. 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. Organizers 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. The Turkish Foreign Ministry condemned the Israeli raid and said it was summoning the Israeli ambassador for an "urgent explanation." Hasan Naiboglu, the Turkish maritime affairs undersecretary, told the Anatolia news agency that Israel had jammed communications with the ships. He accused Israel of violating international law by carrying out the raid in international waters. Turkey had unofficially supported the aid mission and has been vocally critical of Israeli military operations against Palestinians in Gaza. Israel's Ynet news website said Israeli Defense Minister Ehud Barak called Turkish officials, including the defense and foreign ministers, to discuss the raid. 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 U.N. official in the region, Robert Serry. 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. This is the ninth time that the Free Gaza movement has tried to ship in humanitarian aid to Gaza since August 2008. Israel has allowed ships through five times, but has blocked them from entering Gaza waters since a three-week military offensive against Gaza's Hamas rulers in January 2009. The latest flotilla was the largest to date. ___ Goldenberg reported from aboard the Israeli warship INS Kidon. AP writer Selcan Hacaoglu contributed to this report from Ankara.