UNITED NATIONS — Russia's foreign minister is lashing out at countries that are backing opposition groups fighting to overthrow the dictatorship of Syria's Bashar al-Assad, saying that was pushing Syria even deeper into internecine strife.

Russia, Syria's primary backer, and China have blocked three attempts by Western governments to pass United Nations Security Council resolutions that would impose sanctions on the Assad regime.

Sergei Lavrov, the Russian diplomat, told the U.N. General Assembly that the fighting in Syria, which has killed more than 30,000 people, must end through a comprehensive cease-fire, release of prisoners and humanitarian aid.

He said Russia backs the efforts of special U.N. envoy Lakhdar Brahimi to end the fighting. He said the number of war crimes is growing both by the Assad regime and the opposition fighters.