Israeli marines stormed a Turkish aid ship bound for Gaza and at least nine pro-Palestinian 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.
Boarding from dinghies and rappelling from helicopters, naval commandos stopped six ships, 700 people and 10,000 tonnes of supplies from reaching the Islamist-run Palestinian enclave - but bloody miscalculation left Israel condemned.
Besides Turkish crew and passengers on board the Gaza-bound air ship, there were seven German, three US, three Australian, four Bahraini, five Belgian, one Bosnian, 32 Algerian, 12 Indonesian, five Moroccan, two Palestinian, one French, one Dutch, one South African, 28 British, three Irish, three Spanish, five Israeli, five Swedish, two Canadian, one Kosovan, 16 Kuwaiti, three Lebanese, three Macedonian, 11 Malaysian, three Egyptian, three Pakistani, two Mauritanian, four Syrian, one Omani, 31 Jordanian, four Yemeni, one New Zealander and one Greek people aboard the ships, Arinc also said.
Once-close Muslim ally Turkey accused it of "terrorism" in international waters. The UN Security Council met in emergency session. The European Union, a key aid donor to Palestinians, demanded an independent inquiry and an end to the Gaza embargo.
Israel's most powerful friend, the United States, was more cautious, disappointing Turkey. But President Barack Obama said he wanted the full facts soon and regretted the loss of life.
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 that had been planned for Tuesday.
He said his forces had been attacked: "They were mobbed, they were clubbed, they were beaten, stabbed, there was even a report of gunfire. And our soldiers had to defend themselves."
For all his regret, he vowed to maintain a three-year-old embargo to stop Iranian-backed Hamas from bringing arms to Gaza.
Back home, questions were asked about how an operation that aimed to avoid bloodshed had gone so badly and publicly wrong.
The White House meeting had seemed intended to soothe ties with Obama, which have been strained by differences over Jewish settlement expansion that had delayed the recent revival of peace talks with the Palestinians. But Obama must also balance support for Israel, which is popular with American voters, with understanding for an angry Turkey and other Muslim U.S. allies.
Palestinian President Mahmoud Abbas said: "What Israel has committed on board the Freedom Flotilla was a massacre."
Even after the vessels were escorted into Israel's Ashdod port, accounts of the pre-dawn operation some 120 km out in the Mediterranean were sketchy and limited to those from the Israeli side. Activists were held incommunicado, though Israeli officials said most would be free to go in due course.
Military night-vision video showed commandos being winched down, only to be surrounded. Some Israeli commentators asked why commanders put troops into a position where they were cornered.
An Israeli minister admitted plans to maintain the blockade on Hamas while avoiding an international incident had backfired in spectacular fashion. "It's going to be a big scandal, no doubt about it," Trade Minister Binyamin Ben-Eliezer said.
One marine told reporters his squad went in with anti-riot paintball guns but, fearing for their lives, resorted to using normal pistols or leapt overboard. Navy video showed a commando fire a paintball at a man who seemed to be clubbing an Israeli.
Other footage showed a commando fire a pistol, two-handed.
"We were prepared to face human rights activists and we found people who came for war," the marine told reporters.
Israeli military officials said nine activists died on the Mavi Marmara, a Turkish cruise ship carrying nearly 600 people. Most of the dead were Turks, one senior Israeli officer said.
Military officials said some activists had snatched pistols from the boarding party, which responded to gunfire. Seven troops and 20 protesters were injured, the military said. Some officials had earlier put the death toll at 10 or even higher.
A Turkish Islamic charity chartered the Mavi Marmara. Other vessels carried Americans and Europeans, including politicians, a Jewish Holocaust survivor and Swedish author Henning Mankell.
The bloodshed sparked street protests and government ire in Turkey, long Israel's lone Muslim ally in the region.
Prime Minister Tayyip Erdogan, whose Islamist views and outreach to Iran and other Israeli enemies are blamed by many in Israel for souring relations, headed home from Chile.
He said: "This action, totally contrary to the principles of international law, is inhumane state terrorism."
Some said Turkey's political and economic ties with Israel were too deep and complex to suffer serious long-term damage, but Ankara cancelled joint military exercises and recalled its ambassador.
Israel told tourists in Turkey to stay indoors and dismissed any accusations that it had broken international law by boarding foreign ships far beyond its own territorial waters.
Israeli forces were on high alert but aside from scattered scuffles, there was little trouble with Palestinian protesters.
Demonstrations in European cities included Paris, Stockholm, Rome and Athens, where police used tear gas against protesters who threw stones and bottles near Israel's embassy to Greece.
The UN Security Council heard calls from most members for an inquiry. Diplomats then tried to agree on a common statement.
The Arab League condemned what it called a "terrorist act". Iranian President Mahmoud Ahmadinejad called it "inhuman".
More worryingly for Israel, its friends showed little sympathy. The outrage sounded at times more uniformly hostile to the Jewish state than during its offensive in Gaza, which killed 1,400 Palestinians in December 2008 and January 2009.
Israel said it launched that war to curb Hamas rocket fire on its towns. But it has found it harder to win understanding for an embargo limiting supplies to 1.5 million people in Gaza, including cement the UN says it needs to repair bomb damage.