Syrian rebel groups announced on Monday that they had decided to freeze any talks about their possible participation in Syrian peace negotiations being prepared by Moscow in Kazakhstan unless the Syrian government and its Iran-backed allies end what it said were violations of a ceasefire.

In a statement, the rebel groups also said that any territorial advances by the army and Iran-backed militias that are fighting alongside it would end the fragile ceasefire brokered by Russia and Turkey – which back opposing sides – that came into effect on Friday.

“The regime and its allies have continued firing and committed many and large violations,” said the statement signed by a number of rebel groups.

On Saturday the UN security council gave its blessing to the ceasefire deal, which is slated to be followed by peace talks in the Kazakh capital, Astana. The statement said the main violations were in an area north-west of Damascus in the rebel-held Wadi Barada valley, where government forces and the Iran-backed Lebanese Hezbollah group have been trying to press their advances.

Rebels say the Syrian army is seeking to recapture the area, which contains a spring that provides most of Damascus’s water and which lies on a major supply route from Lebanon to the Syrian capital which is used by Hezbollah.

Like previous ceasefire deals in Syria, it has been shaky from the start, with repeated outbreaks of violence in some areas, but it has largely held.

The rebel groups questioned Russia’s ability to force the Syrian government and their allies to abide by the terms of the ceasefire deal.