The Syrian government pushes ahead with its military crackdown while mourners gather daily to mark the passing of new victims. NBC News' Ayman Mohyeldin reports from Cairo.
Updated at 5:03 p.m. ET: UNITED NATIONS -- The U.N. human rights chief decried Syria's escalating crackdown on civilian protesters Monday and warned that the Security Council's failure to take action has emboldened the Syrian government to launch an all-out assault to crush dissent.
Navi Pillay expressed fears that the deliberate stirring of sectarian tensions may plunge Syria into civil war. She said there are strong indications of ongoing crimes against humanity and again appealed for President Bashar Assad's government to be referred to the International Criminal Court.
Standing before the 193-member General Assembly, Pillay said tens of thousands of people, including children, have been arrested, more than 18,000 reportedly are still arbitrarily detained, and thousands more are reported missing. Another 25,000 people are estimated to have sought refuge in neighboring countries, and more than 70,000 are estimated to be internally displaced, she added.
The General Assembly is expected to consider a nonbinding resolution similar to the Security Council resolution that Russia and China vetoed on Feb. 4.
"The failure of the Security Council to agree on firm collective action appears to have emboldened the Syrian government to launch an all-out assault in an effort to crush dissent with overwhelming force," she said.
Earlier on Monday, Russian Foreign Minister Sergei Lavrov said Moscow would not support a plan to send U.N. peacekeepers into Syria unless there was a halt to violence by both government forces and their armed opponents.
Lavrov said Russia was studying the proposal for a joint United Nations-Arab peacekeeping force in Syria, announced on Sunday at an Arab League meeting in Cairo, and wanted more details.
But his remarks suggested his country, which has veto power at the U.N. Security Council, would use the proposal to underscore its own argument that the government's armed opponents are no less of an obstacle to peace than Syrian President Bashar Assad's forces.
U.N. peacekeeping missions "need to first have a peace to support," Lavrov told a news conference after talks with United Arab Emirates Foreign Minister Sheikh Abdullah bin Zayed al-Nahyan.
"In other words, it is necessary to agree to something like a cease-fire, but the tragedy is that the armed groups that are confronting the forces of the regime are not subordinate to anyone and are not under control," Lavrov said in Moscow.
Russia joined China on February 4 in a double veto to block a U.N. Security Council resolution supporting an Arab League call for Assad to quit, provoking strong criticism from the Western and Arab sates that supported the draft.
Lavrov, who met Assad in Damascus three days after the veto, said he told the president the violence - which the United Nations says has killed more than 5,000 people since the start of a state crackdown on protests almost a year ago - must stop.
However, he emphasized Monday, this "also applies to the armed groups opposing the regime, which use modern guns, mortars and grenade launchers and also sow death."
"A halt to the violence ... must be universal, no matter where it comes from," Lavrov said. "So there needs to be a mechanism for the realization of this most important, key, primary principle."
Russia has been increasingly isolated in its support for Assad, whose government has given Moscow its strongest post-Soviet foothold in the Middle East by buying arms and hosting a naval maintenance and supply facility.
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Reuters and The Associated Press contributed to this report.