Although the report has not yet been officially released, Turkey's President Abdullah Gul said his country would reject it, regarding it as "null and void".
The report says that the Israeli special forces "faced significant, organized, and violent resistance from a group of passengers", but that "most of the deceased were shot multiple times, including in the back, or at close range."
It added that the flotilla "acted recklessly in attempting to breach the naval blockade", but called on Israel to make an "appropriate statement of regret" and pay compensation to the families of the dead.
The Israeli government says it will not apologise, though it has indicated that it would accept most of the report's conclusions "with specific reservations", while emphasising that the text noted its legal right to blockade Gaza.
But Turkey's foreign minister said today that Ankara plans to challenge the Gaza blockade at the International Court of Justice in The Hague, the highest court of the United Nations.
Turkey recalled its own ambassador from Tel Aviv in the immediate aftermath of the Israeli assault on the Mavi Marmara boat, during which eight Turkish citizens, and one American of Turkish descent died.
Turkey has repeatedly said it will not restore normal relations with Israel unless Israel apologises and compensates victims.
Turkey was one of Israel's rare allies in the Muslim world, but relations have deteriorated under the leadership of Recep Tayyip Erdogan who has been Prime Minister since 2002.