The death toll in Syrian protests rose as long-time Damascus ally Russia said President Bashar al-Assad had made "a lot of mistakes" in clamping down on the year-old demonstrations.
Fresh clashes broke out in the capital and security forces killed at least 30 people, all but two of them civilians, in violence elsewhere across the country, the Syrian Observatory for Human Rights said.
The capital's security clampdown follows what activists said was a hit-and-run attack in the heavily guarded Mazzeh neighbourhood on Monday that killed at least three rebels and a member of the security forces.
It also came on the heels of deadly twin suicide car bombings targeting security buildings in Damascus on Saturday.
The violence, however, is not all one-sided: Syria's armed opposition is kidnapping, torturing and executing security force members and government supporters, according to the New York-based Human Rights Watch.
"The Syrian government's brutal tactics cannot justify abuses by armed opposition groups," said Sarah Leah Whitson, HRW's Middle East director.
"Opposition leaders should make it clear to their followers that they must not torture, kidnap, or execute under any circumstances."
The rights watchdog group said the peaceful uprising had transformed into an armed insurgency, especially since early February, when the government attacked opposition strongholds throughout the country.
The Syrian National Council deplored the reported rights violations.
"We oppose any form of violence and support all the international conventions and treaties on the protection of human rights," the SNC said in a statement issued by spokeswoman Bassma Kodmani.
Russian Foreign Minister Sergei Lavrov said Assad had made "a lot of mistakes" since peaceful protests began in March 2011.
"We believe that the Syrian leadership responded incorrectly to the very first manifestations of the peaceful protests," he told Russia's Kommersant FM radio in a pre-recorded interview.
"The Syrian leadership -- despite the numerous promises it has made in response to our calls -- is making a lot of mistakes."
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Russia has increasingly hinted it could drop its support for Assad after a year of violence that Syrian opposition activists say has claimed more than 9,100 lives.
Russia said it was ready to back either a UN Security Council statement or resolution on UN-Arab League peace envoy Kofi Annan's proposal on ending the crisis as long as it contained no ultimatums.
Last week, Lavrov also accused Assad of making errors and moving too slowly on reforms, but the latest comments suggest that Russia was unhappy with his leadership from the early stages of the bloody conflict.
Lavrov even hinted that Moscow would not be opposed to the idea of Assad being offered safe haven by another country.
"Perhaps that is the case, but that is something for Assad to decide," he said in response to a question about whether Syria's president should step down before being toppled and killed like Libyan dictator Moamer Kadhafi.
At the United Nations, diplomats from the 15-nation Security Council held four hours of talks on a Western-drafted presidential statement seeking to reinforce international backing to Annan's efforts to halt the bloodshed.
Russia led resistance to part of the statement that said the council would "consider further measures" if Assad does not act upon the envoy's peace plan, diplomats said. Russia and China have already vetoed two full resolutions on Syria.
With no agreement made, the talks moved up to ambassador level. "There are major political issues at stake so we will see whether we can solve them," French envoy Gerard Araud told reporters as he entered the talks.
The proposed statement, obtained by AFP, does not condemn the violence but would express "gravest concern" at the deteriorating crisis in Syria and "profound regret" at the thousands of dead.
Araud had expressed hope that the statement -- which carries less weight than a full resolution -- could be adopted on Tuesday.
In Geneva, Annan briefed Arab League chief Nabil al-Arabi on the mission in Damascus, UN spokeswoman Corinne Momal-Vanian said.
"Both men underscored the importance of a unified message from the international community," Momal-Vanian said.
Separately, UN officials named former peacekeeping chief Jean-Marie Guehenno as a deputy to Annan in his mission to end the Syrian crisis.
French-born Guehenno joins former Palestinian diplomat Nasser al-Qudwa as Annan's deputies on the tough mission.