Syria's main opposition alliance, the National Coalition, said it had decided not to attend a summit of the Friends of Syria in Rome next month, and also turned down invitations for talks in Washington and Moscow.
In a statement, the coalition said:
"The international silence on the crimes committed every day against our people amounts to participating in two years of killings,"
"The Russian leadership especially bears moral and political responsibility for supplying the regime with weapons."
Further singling out rage over Russia's supply of missiles to Assad's regime, the statement said:
"Hundreds of civilians have been killed by Scud missile strikes and Aleppo is being systematically destroyed."
See BBC News for full report.