Israel faced a global diplomatic firestorm Monday over its deadly raid on a protest flotilla carrying humanitarian aid that was attempting to break through an Israeli blockade of the Gaza Strip.

Amid demonstrations erupting worldwide, foreign leaders and protest organizers accused Israel of using excessive force in the raid in international waters. At an emergency meeting, the United Nations Security Council condemned the violence and called for an investigation.

Israel defended its actions, saying its soldiers were ambushed with knives and metal bars — as well as handguns wrested from the commandos — during the late-night raid, which occurred about 40 miles off Israel’s coast.

The Israeli military said nine protesters were killed. Protest organizers put the death toll at 16. Dozens were wounded, including seven Israeli soldiers.

Video of the raid released by the Israeli military, Turkish television and other media sources depicted a dramatic high-seas brawl in which Israeli commandos rappelled from helicopters onto a ship and immediately clashed with activists on board.

Responding to the brewing crisis, Israeli Prime Minister Benjamin Netanyahu cut short his visit to Canada to return to Israel, cancelling a much-anticipated White House visit with President Obama scheduled for Tuesday that been widely seen as an opportunity to show improved U.S.-Israeli ties.

The Israeli raid appeared to be a public relations nightmare for Israel, putting the Obama administration in an awkward position just as it hoped to put to rest a frosty period in its alliance with Israel.

Whereas most governments used harsh language to condemn the raid, the administration responded cautiously, expressing regret at the loss of life but stopping short of criticizing Israel until full details of the incident are known.

The global focus on Israel’s conduct in the raid — including the attention of the U.N. Security Council — now threatens to be a distraction from the U.S. administration’s diplomatic priorities, notably getting international consensus for sanctions to deal with Iran’s nuclear program.

Despite the international outrage directed at Israel, a senior administration official said Washington would strive to keep Arab states committed to the peace process.

“There will be tensions here, but the real key will be keeping political support for the talks intact,” said the official, who spoke on condition of anonymity. “That will be our challenge.”

The immediate focus of the international community, however, is now squarely on Israel’s blockade of Gaza, which had slid into the background of international issues.

On Monday, world leaders decried the interception of the pro-Palestinian convoy, which was attempting to bring food, medical supplies, clothing and construction supplies to the impoverished territory.

French President Nicolas Sarkozy criticized Israel’s “disproportionate use of force.” U.N. Secretary-General Ban Ki-moon condemned the violence. The European Union’s foreign affairs chief, Catherine Ashton, said the bloc was deeply concerned, and she called on Israel to conduct an inquiry. British Foreign Secretary William Hague deplored the killings and called for an end to the Gaza blockade.

Turkish Foreign Minister Ahmet Davutoglu called the raid “banditry and piracy” on the high seas and “murder conducted by a state.” Turkey, whose citizens accounted for more than half the flotilla’s passengers and which has been an ally of Israel, recalled its ambassador to Israel and warned of further actions.

Ma Zhaoxu, China’s Foreign Ministry spokesman, said his nation “is appalled and condemns the Israeli navy’s attack on the Turkish fleet shipping humanitarian aid to the Gaza Strip.”

Greece, Egypt, Sweden, Spain and Denmark summoned Israel’s ambassadors, demanding explanations for the violence. Greece suspended a military exercise with Israel and postponed a visit by Israel’s air force chief. Germany called for an immediate investigation but was careful not to directly place blame, adding that it was seeking information on six German citizens believed to have been aboard the ships.

Riot police used tear gas to drive back hundreds of protesters demonstrating outside the Israeli Embassy in Paris. There were also demonstrations in the U.S., Britain, Italy, Sweden, Norway, Cyprus and more than 20 cities in Greece.

At the United Nations, Palestinians and Arabs, backed by a number of Security Council members, called for Israel to lift the blockade on Gaza, immediately release the seized ships and activists, and allow them to deliver their goods.

After the raid, Israel’s navy escorted the six vessels in the flotilla to the Israeli port of Ashdod, where the government had set up tents to accommodate the activists. Protesters were offered the choice of flying home immediately or facing arrest and imprisonment. By Monday evening, most were opting to be arrested, officials said, with as many as 600 activists from 40 nations still being held.

The Israeli military did not permit any of the detained passengers to speak to reporters or communicate with family members. The passengers include members of the European Parliament, journalists and artists.

No information had been released about the identities of those killed. Several dozen activists were being treated in Israeli hospitals.

Israeli officials Monday said their soldiers had expected moderate resistance and civil disobedience but instead encountered organized attacks the moment the commandos rappelled onto the Turkish-flagged Mavi Marmara, the lead ship in the flotilla, with more than 500 passengers.

“They beat us up with metal sticks and knives,” said one Israeli commando, speaking on condition of anonymity.

Soldiers had been ordered to treat the raid as a “police action” and use only paintball rifles to control the crowds, according to a report by Ynet, an Israeli news website. But as the first soldiers boarded, they were quickly beset by protesters allegedly using switchblades, slingshots, deck chairs, marbles, metal balls and metal bars, military officials said.

According to the military, two protesters grabbed handguns from two commandos and began firing.

“There was live fire at some point against us,” the commando said. “They were shooting at us from below deck.”

At least one soldier was thrown from the top deck of the boat to the lower deck by activists, according the commando and video released by the military. Some soldiers jumped into the water to escape, the commando said.

At some point, military commanders authorized soldiers to use handguns against the crowds, military officials said.

“Soldiers acted appropriately in this situation,” said the military’s chief of staff, Gaby Ashkenazi. “Soldiers found themselves in a life-threatening situation and used their weapons.”

Two soldiers suffered gunshot wounds and one was stabbed, officials said.

Israeli Deputy Foreign Minister Danny Ayalon called the flotilla an “armada of hate and violence” that launched a “premeditated and outrageous provocation.”

Protest organizers gave a dramatically different version of events, insisting that activists were unarmed and that Israeli soldiers began shooting as soon as they boarded.

Leaders of Free Gaza, one of the pro-Palestinian groups that organized the flotilla, said Israeli soldiers launched an “illegal” night raid while the flotilla was still in international waters.

“They can spin it any way they want,” said Greta Berlin, a Free Gaza leader, speaking from the group’s office in Cyprus. “We’re the civilians and they are the military. This was murder.”

The group has been unable to contact its members since the attack began because Israel has jammed telephone signals.

Palestinian negotiator Saeb Erekat called Israel’s action a “war crime,” but he also told Al Jazeera television that he saw no need to pull out of peace negotiations being mediated by the U.S.

The Arab League, which represents 22 countries, released a statement assailing “this terrorist act” and called for an “urgent meeting,” which is expected to be held Tuesday.

Lebanese Prime Minister Saad Hariri called the Israeli action “a dangerous and crazy step that would inflame the struggle in the region.”

In Israel, opposition leaders rallied to support the government in a sign of national unity. But some Israelis called on the government to reevaluate the blockade.

“It’s a crime,” Israeli Arab lawmaker Ahmad Tibi said. “Israel feels like it lives above international law and can do whatever it wants.”

But Ayalon, accusing some of the protesters of having links with terrorist groups, defended the boats’ seizure.

“Allowing these ships to go in an illegal way to Gaza would have opened a corridor of smuggling arms and terrorists to Gaza,” he said.

Israel has maintained a blockade against Gaza since 2007 to protest the territory’s takeover by the Palestinian militant group Hamas.

edmund.sanders@latimes.com

Batsheva Sobelman of The Times’ Jerusalem Bureau, Times staff writers Jeffrey Fleishman in Cairo and Peter Nicholas in Washington and special correspondent Meris Lutz in Beirut contributed to this report. Times wire services were also used.