JERUSALEM - Israeli commandos rappelled down to an aid flotilla sailing to thwart a Gaza blockade on Monday, clashing with pro-Palestinian activists on the lead ship in a botched raid that left at least nine passengers dead.

Bloodied passengers sprawled on the deck and troops dived into the sea to save themselves during several hours of hand-to-hand fighting that injured dozens of activists and six soldiers. Hundreds of activists were towed from the international waters to Israeli detention centers and hospitals.

International condemnation was swift and harsh as Israel scrambled to explain how what was meant to be a simple takeover of a civilian vessel went so badly awry.

Israeli Prime Minister Benjamin Netanyahu abruptly canceled a planned meeting with President Barack Obama in Washington to rush home. The global reaction appeared likely to increase pressure to end the embargo that has plunged Gaza's 1.5 million residents deeper into poverty.

Most of the information about what happened on the single ship where violence broke out came from Israel, which cut off all communication to and from the activists and provided testimony and video evidence that its soldiers came under attack by activists armed with metal rods, knives, slingshots and two pistols snatched from the troops.

Passengers reached at an Israeli hospital and journalists aboard the ship accused the soldiers of using excessive force. One passenger, who identified himself as American, spoke briefly with reporters.

"I'm not violent. What I can tell you is that there are bruises all over my body. They won't let me show them to you," he said before he was pushed away by a security escort.

A soldier identified only as a sergeant told reporters at a military briefing that the activists on board "were armed with knives, scissors, pepper spray and guns." He said he was armed only with a paintball rifle. "It was a civilian paintball gun that any 12-year-old can play with," he said. "I saw my friends on the deck spitting blood."

The high-seas confrontation was a nightmare scenario for Israel, which insisted its soldiers were simply unprepared for what awaited them on the Mavi Marmara, the ship carrying 600 of the 700 activists headed for Gaza. Instead of carrying their regular automatic rifles, the Israelis said they went in with non-lethal paintball guns and pistols they never expected to use.

Israel intercepted the six ships carrying some 10,000 tons of aid for the isolated seaside territory, which has been blockaded by Israel for three years, with Egypt's cooperation. The Israeli government had urged the flotilla not to try to breach the blockade before the ships set sail from waters off Cyprus on Sunday and offered to take some aid in for them.