8 massacres by Syria regime and 1 by rebels since April 2012, U.N. war crimes report shows

GENEVA Evidence confirms at least eight massacres have been perpetrated in Syria by President Bashar Assad's regime and supporters and one by rebels over the past year and a half, a U.N. commission said Wednesday.

Calling Syria a battlefield where "massacres are perpetrated with impunity," the U.N. commission investigating human rights abuses in Syria said that in each of the incidents since April 2012 "the intentional mass killing and identity of the perpetrator were confirmed to the commission's evidentiary standards."

Its latest report Wednesday also notes that the four-member commission is probing nine more suspected mass killings since March. With those, it said, the illegal killing was confirmed but the perpetrator could not yet be identified. In other cases, it said, the circumstances of the killing were not sufficiently clear to be able to determine the legality.

The report updates the commission's work since 2011 to mid-July, stopping short of what the United States says was an Aug. 21 chemical weapons attack on rebel-held areas that killed hundreds of civilians.

On Tuesday, the group Human Rights Watch issued a report that said evidence strongly implies that Syrian government troops' firing of rockets contained a nerve agent during that Aug. attack.

The commission created by the U.N.'s 47-nation Human Rights Council says both sides have committed heinous war crimes during the 2 ½-year conflict that has killed over 100,000 people. The council is due to take up the report and the commission plans to hold a news conference next week.

"Because negotiations are ongoingto find common ground between Russia and the U.S., U.K. and France on the U.N. Resolution to secure Syria's chemical weapons, the U.N. Independent International Commission of Inquiry on the Syrian Arab report, released today with evidence of war crimes by the Assad government and the rebels, is weighing on the talks, because the West wants to call for accountability," reports CBS News' Pamela Falk, from the U.N.

"The report calls for accountability and Russia rejects any referral to the International Criminal Court," Falk added.

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In a statement accompanying the report, the commission chaired by Brazilian diplomat and scholar Paulo Sergio Pinheiro said most casualties result from unlawful attacks using conventional weapons and any response to end the conflict "must be founded upon the protection of civilians."