Meanwhile, the American Jewish Committee condemned the pro-Hamas "Free Gaza" movement and its supporters for deliberately provoking a violent confrontation with the Israeli Navy early Monday morning.
Jeremy Ben-Ami, president of the liberal J Street lobby, said in a statement issued Monday that "A credible, independent commission appointed by the Israeli government should provide the world with a full and complete report into the causes and circumstances surrounding the day's events and establish responsibility for the violence and bloodshed."
Ben-Ami called on President Obama and other international leaders to use this "as an opportunity to engage even more forcefully in immediate efforts to end the Israeli-Palestinian conflict."
J Street was "shocked and saddened" by reports of the killed and wounded international activists and Israel soldiers, the statement said.
Nine activists and several dozen protesters aboard a flotilla of ships bound for Gaza were killed during rioting after Israeli naval forces boarded the ships to redirect them to an Israeli port. The flotilla was attempting to break the Israeli Navy's blockade of the strip. Seven Israeli soldiers were injured.
Americans for Peace Now called on Israel "to thoroughly investigate the operation and to reassess its policy toward the Gaza Strip."
The organization also joined the Israel-based Peace Now "in expressing outrage at the way Israel’s government is dealing with people who challenge its policies," noting that Peace Now activists on Monday were demonstrating against Israeli government policies in Tel Aviv.
"The details of the operation in the Mediterranean are still not clear," APN President and CEO Debra DeLee said. "Regardless, the outcome of this operation is unacceptable and the policy that led to it is deeply flawed.
She added, "The fact that Israel finds itself in this difficult situation today underscores the extent to which Israel’s continued policy of blockading Gaza in untenable and increasingly indefensible.”
DeLee criticized Israeli officials for calling challenges to its policies as terrorism, saying that "such language cheapens the debate and undermines Israel’s legitimate position when it acts in genuine self-defense."
Peace Now Secretary General Yariv Oppenheimer chided Israel in a statement published on Israeli daily Ma'ariv's website, saying that "Even if the fleet to Gaza is irritating and outrageous, a sovereign state cannot treat every act of protest as a terror event that has to end in bloodshed."
"If the miserable naval clash had any winners, they are in Tehran, in the bunkers of Beirut and in the Hamas headquarters in Gaza. The Hamas government succeeded with the Israeli government's active support to receive international recognition, to gain the support of the Arab world and to be seen as a hero standing up to Israel," Oppenheimer said.
The American Jewish Committee in its condemnation of the protesters said the tragedy could have been avoided and regretted the loss of life.
"The fact that the flotilla refused to cooperate with Israel's repeated entreaties to unload their humanitarian cargo in Ashdod for delivery to Gaza proves that violent clashes are exactly what the international supporters of Hamas must have been seeking," said AJC Executive Director David Harris.