JERUSALEM (CNN) -- The Israeli military on Monday rejected allegations that its soldiers committed atrocities against Palestinians in Gaza.

Israel says the majority of Palestinians killed during "Operation Cast Lead" were "terror operatives."

The conclusion follows a military police investigation into claims made at a conference that the army had intentionally killed civilians and damaged property during Israel's incursion into Gaza in December and January.

Israeli military advocate general Brig. Gen. Avichai Mendelblit concluded "the stories told were purposely exaggerated and made extreme, in order to make a point with the participants of the conference."

The allegations were "based on hearsay " and were "not supported by the facts as determined by the investigation," Mendelblit said in a statement.

Israeli human rights organizations condemned the speed with which military police reached their conclusion.

"The speedy closing of the investigation immediately raises suspicions that the very opening of this investigation was merely the army's attempt to wipe its hands of all blame for illegal activity during Operation Cast Lead," as the Gaza operation was called, nine human rights groups said in a joint statement.

They reiterated their call for a civilian investigation, which Attorney General Menachem Mazuz has rejected.

"The closing of the Army's own investigation only strengthens the need for the attorney general to allow for an independent non-partisan investigative body to be established in order to look into all Israeli Army activity during Operation Cast Lead," said the organizations.

The groups -- The Association for Civil Rights in Israel, Bimkom, B'tselem, Gisha, Hamoked, The Public Committee Against Torture, Yesh Din, Physicians for Human Rights, and Adalah -- said accounts by Palestinians raise the possibility that acts by the military were worse than previously suspected.

Israeli soldiers said earlier this month Palestinian civilians were killed and Palestinian property intentionally destroyed during Israel's military campaign in Gaza, according to Haaretz, an Israeli newspaper.

About 1,300 Palestinians died during "Operation Cast Lead," which aimed to stop militants from firing rockets into Israel from Gaza.

The accounts in Haaretz were from Israeli soldiers who graduated from a pre-military course at an Israeli college. In them, Israeli soldiers complain that the rules of engagement often defied logic and left the impression with Israeli troops that "inside Gaza you are allowed to do anything you want."

None of the soldiers who alleged the wrongdoing admitted taking part in those acts themselves.

The country's top general had already dismissed the claims.

"I don't believe that soldiers serving in the IDF hurt civilians in cold blood, but we shall wait for the results of the investigation," Lt. Gen. Gabi Ashkenazi said last week. He blamed Hamas, the militant Palestinian group which runs Gaza, for choosing "to fight in heavily populated areas.

"It (was) a complex atmosphere that includes civilians and we took every measure possible to reduce harm of the innocent," he said, according to an IDF statement.

There have been numerous allegations of Israeli atrocities during the three-week campaign, including the charge that Israel fired white phosphorus shells "repeatedly over densely populated areas."

Human Rights Watch made the accusation in a report last week.

White phosphorus burns on contact with oxygen. It is legal to use as an illuminant, but the human rights organization alleges that Israel used it as a weapon.

Israel has rejected those claims as well. Other Israeli investigations into the conduct of its troops in Gaza continue.

A United Nations report released last week also criticized the Israeli military's actions during the offensive in Gaza. It said that Israeli soldiers routinely and intentionally put children in harm's way during their 22-day offensive.

The report said investigators had documented and verified reports of violations "too numerous to list."

A spokesman for the Israeli prime minister called the report another example of the "one-sided and unfair" attitude of the U.N. Human Rights Council, which requested it.