A United Nations panel of investigators has found that Israel was in serious breach of international law when it raided a humanitarian aid flotilla headed to the Gaza Strip in late May.

In a report issued Wednesday, three judges nominated by the U.N. Human Rights Council said that a "series of violations of international law, including international humanitarian and human rights law" were committed by Israeli forces during the May 31 interception of a six-ship flotilla which left nine civilians dead.

"[The raid] constituted grave violations of human rights law and international humanitarian law," the 56-page report said.

The judges further noted that the Israelis demonstrated "totally unnecessary and incredible violence" against the passengers and that the raid was motivated in part by "concerns about the possible propaganda victory that might be claimed by the organizers of the flotilla."

"[The raid] betrayed an unacceptable level of brutality. Such conduct cannot be justified or condoned on security or any other grounds," the report stated.

Israel, however, which maintains that its soldiers acted in self-defense, dismissed the council's findings as being "biased and as one-sided as the body that has produced it," and accused the Human Rights Council as taking a "politicized and extremist approach."

"The Human Rights Council blamed Israel prior to the investigation and it is no surprise that they condemn after," Israeli officials said.

Israel is currently conducting its own probe into the flotilla incident parallel to a separate inquiry launched by U.N. General Secretary Ban Ki-moon.

The U.N. judges is scheduled to be submitted to the Human Rights Council on Sept. 27.