JERUSALEM — An Israeli probe ruled Sunday that a deadly May 2010 raid on a flotilla of Gaza-bound aid ships, which killed nine Turkish activists and soured ties with Ankara, did not violate international law.

However, a Turkish probe into the incident, which also released its preliminary findings Sunday, ruled that Israeli troops used "disproportionate" force in boarding the aid ships to prevent them from reaching Gaza.

The bloody assault earned the Jewish state international censure, prompting Israeli lawmakers to appoint a commission headed by former judge Yaakov Tirkel to examine the legality of the military operation as well as Israel's blockade of the Gaza Strip.

In its report released on Sunday, the six-member Tirkel commission concluded that both the raid and the blockade complied with international law.

"The naval blockade imposed on the Gaza Strip... was legal pursuant to the rules of international law," the panel said.

"The actions carried out by Israel on May 31, 2010, to enforce the naval blockade had the regrettable consequences of the loss of human life and physical injuries," the report said.

"Nonetheless... the actions taken were found to be legal pursuant to the rules of international law."

The commission said Israeli troops "encountered extreme violence" when they boarded the Turkish-flagged Mavi Marmara, a ferry carrying around 600 people, which led the six-ship flotilla.

A group of activists from the Turkish Islamist IHH organization on board the ship "used firearms against the (Israeli) soldiers during the hostilities," the report said.

But a separate probe by Turkish investigators concluded that Israeli troops used excessive force during the raid.

"The force used to intercept the Mavi Marmara exceeded the limits of what was appropriate and necessary," the Turkish commission's report, released in Istanbul on Sunday, concluded.

The commission, set up by Turkey last year, interviewed Turkish and foreign activists on the flotilla.

Its preliminary report criticized the "disproportionate nature of the attack" and called on Israel to pay compensation to the families of the victims.

The Mavi Marmara was the biggest of the vessels in the group attempting to break Israel's blockade on the Gaza Strip, which was imposed in June 2006, after Gaza militants kidnapped an Israeli soldier.

The restrictions on imports and exports were tightened a year later when Hamas seized power in the territory of 1.5 million people, ousting its Fatah rivals.

The Israeli commission has heard testimony from high-ranking Israeli officials, including Prime Minister Benjamin Netanyahu, Defence Minister Ehud Barak and army chief General Gabi Ashkenazi.

None of the soldiers who actually participated in the raid were authorized to testify.

Giving evidence in Jerusalem last year, Barak called the flotilla a "planned provocation" and said top officials had suspected its organizers were "preparing for an armed conflict to embarrass Israel."

"We regret any loss of life," he told the Tirkel commission. "But we would have lost more lives if we had behaved differently."

Two other panels are examining the incident.

The United Nations Human Rights Council quickly formed its own inquiry panel, with which Israel refused to cooperate, deeming the council hopelessly biased against the Jewish state.

In August 2010, UN Secretary General Ban Ki-moon named his own panel to investigate, chaired by New Zealand former prime minister Geoffrey Palmer, and with representatives from both Israel and Turkey.