Moscow: Russia insists that terrorist acts in Syria should be investigated with UN and Arab League representatives, the Russian Foreign Ministry said.
The ministry referred in particular to the mass killing of civilians in the Damascus suburb of Daraya, where, it said, more than 200 bodies were found.
"This is yet another crime of a provocative nature," the ministry said in a statement.
"Moscow resolutely condemns these barbarous acts of violence. At the same time, we insist on a thorough and unbiased investigation into all the circumstances of the recent tragedies," it said.
"All those guilty of these crimes should go on trial and be punished severely," it said.
The ministry reiterated that there was no alternative to Kofi Annan`s peace plan and the Geneva accords.
Citing opposition activists, Al Arabiya TV channel reported that more than 300 people were killed in Daraya.
The opposition alleged that the people were executed during a military operation by government troops on August 25.
Since it began with demonstrations against President Bashar al-Assad`s regime in March 2011, the Syrian conflict has claimed up to 20,000 lives, according to estimates by various groups.