Syria's key opposition National Coalition said Sunday it will boycott talks proposed by UN peace envoy Staffan de Mistura because of concerns over his plan and Russia's air strikes in Syria.

The National Coalition has "decided not to participate in the consultative working groups and considers adherence to the Geneva communique and (UN) Security Council resolutions and an end to Russian aggression to be the basis for the resumption of the negotiation process," it said in a statement.