NEW YORK — A U.N. panel has concluded that Israel’s armed raid on a flotilla carrying Turkish and other foreign activists and humanitarian supplies toward the Gaza Strip last year was legal, but that its use of force in an operation that left nine people dead, including an American citizen, was “excessive and unreasonable.”

The 105-page report — written by Sir Geoffrey Palmer, a former New Zealand prime minister, and Alvaro Uribe, Colombia’s former president — concluded that Israel has a legal right to maintain a naval blockade of Gaza. But it called on the Israeli government to offer a public expression of “regret” for the loss of life on the Mavi Marmara, where the most violent clashes occurred, and to pay compensation to the families of the dead.

The Israeli raid on the flotilla, which was organized in Turkey, threatened to torpedo one of the most important diplomatic alliances to emerge in the Middle East: the rapprochement between Israel and Turkey, one of the region’s most important Islamic governments and a U.S. ally.

U.N. Secretary General Ban Ki-moon established the panel, with the approval of Israel and Turkey, in an effort to help to reconcile differing accounts of events on the flotilla from Israel and Turkey, and to help patch up strained diplomatic relationships between the two countries.

Israel and Turkey appointed representatives to serve on the panel, but without the authority to block the report’s publication. The Israeli and Turkish members of the panel objected to select findings that had undercut their governments’ respective positions.

The report concluded that “Israel faces a real threat to its security from militant groups in Gaza” and had imposed the naval blockade “as a legitimate security measure” to prevent weapons from entering Gaza by sea. Israeli commandos “faced significant, organized and violent resistance from a group of passengers when they boarder the Mavi Marmara, requiring them to use force for their own protection,” the report found.

The report concluded that the “majority of flotilla participants had no violent intentions, but there exist serious questions, conduct, true nature and objectives of the flotillas organizers.”

Still, the panel provided a far more damning account of the conduct of Israel Defense Forces during and after the raid. “Israel’s decision to board the vessels with such substantial force at a great distance from the blockade zone and with no final warning immediately prior to the boarding was excessive and unreasonable,” according to the report. “The loss of life and injuries resulting from the use of force by Israeli forces during the takeover of the Mavi Marmara was unacceptable.”

The Israeli government declined to make an official comment Thursday afternoon, but an official who spoke on the condition of anonymity said: “The report clearly endorses Israel’s position regarding the legality of the naval blockade and its enforcement. We accept the report and its recommendations and we hope that Turkey will do the same, opening a new possibility for reconciliation in spite of everything. ... The bottom line for us is that globally the whole flotilla should not have sailed at all, and relations with Turkey must be mended according to the recommendations of the committee.”

The report stated that the Israeli government had failed to provide a “satisfactory explanation” as to how and why the nine passengers were killed in the incident in late May 2010. “Forensic evidence showing that most of the deceased were shot multiple times, including in the back, or at close range has not been adequately accounted for in the material presented by Israel,” it concluded.

Israel has rejected a Turkish demand that it apologize for the deaths caused by its raid on the flotilla, despite pressue from Washington to do so.

The report is scheduled to be released Friday by the United Nations. The New York Times, which obtained a copy of the report, published a story on the findings on its Web site earlier today. The report was finished months ago, but the United Nations has delayed its release numerous times.

The Israeli representative on the panel, Joseph Ciechanover Itzhar, wrote in a letter attached to the report that he supported the report’s release, and that Israel welcome the panel’s conclusion that the naval blockade is legal.

But he said Israel had “reservations” about aspects of the report, particularly the claim that Israel had used excessive force and failed to provide adequate warning. He said the panel was “provided evidence of the repeated warning it gave the vessels.”

He said the panel’s chief authors did not “adequately take into account the complexities” of a combat operation where efforts to reconstruct “the exact chain of events is extremely difficult, if not impossible. Given the close range combat that clearly took place aboard the vessel, wounds sustained at close range do not in themselves suggest wrongdoing by Israeli soldiers.”

Turkey’s representative to the panel, Suleyman Ozdem Sanberk, registered his “disagreement” with several of the reports’ conclusions, including its finding that the naval blockade is legal. “Freedom and safety of navigation on the high seas,” he said, “is a universally accepted rule of international law. There can be no exception from this long-standing principle unless there is a universal convergence of views.”

He also insisted that the “report was not satisfactory in describing the actual extent of the atrocities that the victims had been subjected to…They came under attack on international water. They resisted for their own protection.”

Greenberg reported from Jerusalem.