Russia is urging Syrian rebels to separate themselves from "terrorists" to ensure that the Russia-US-brokered cease-fire continues to hold.
A spokesman for Russian President Vladimir Putin said the Kremlin is hopeful that the truce deal "will create the necessary environment for political settlement".
Dmitry Peskov told reporters that the Kremlin welcomes the ceasefire, but that the key thing now is to make sure moderate opposition groups are separated from the "terrorists" - a reference to militant groups such as Syria's al-Qaida affiliate.
Mr Peskov said that is the "key task, without which further progress can hardly be possible".
Russia launched its operation in Syria last year to support ally President Bashar Assad's forces.