Russia has said US-backed rebels have repeatedly violated the ceasefire deal.

"Syrian government forces have stopped fire completely in all areas, apart from where ISIL and Jabhat al Nusra fighters are operating. Unfortunately, we can't say the same about the armed groups of moderate opposition controlled by the US," said Lieut. Gen. Viktor Poznikhir, Russian General Staff official.

"Since the ceasefire came into force and until this morning, we registered 23 cases of shelling coming from their side and directed at residential districts and government army positions."