The Syrian army and allied forces also clashed with rebel fighters while trying to advance on a frontline town near the strategic Jabal al-Akrad mountain range, said Jaish al-Nasr and the British-based Syrian Observatory for Human Rights.
An opposition tracking center that monitors military aircraft movements said the airstrikes by Russian warplanes had stopped by the early afternoon.
There was no mention of the operation on Russian or Syrian news agencies.
Moscow has long backed Syria's President Bashar al-Assad in his nine-year-old war against rebels. Russia has an air base in Latakia.
The Syrian army has launched several campaigns to try to seize the Kubayna mountain in Jabal al-Akrad. The eviction of rebels from commanding positions in the mountains would bring the army closer to securing parts of Idlib, in the northwest, and a main highway connecting the cities of Latakia and Aleppo.
The northwest is home to a mix of Islamist militant and opposition groups, many of which fled other parts of Syria as Assad, with Russian backing, seized back territory from them in the civil war that erupted after a crackdown on protests in 2011.The area is also populated by hundreds of thousands of internally displaced persons who rely heavily on humanitarian assistance.