Russian warplanes have mounted a new wave of air strikes since Thursday night in northwestern and western Syria, a Syrian military source and state TV said on Friday.
The source said the 18 air strikes were in the provinces of Idlib, Hama and Aleppo and were against Islamic State targets.
The air strikes however appeared at least partly focused on areas hit earlier this week by the Russians where Islamic State has little or no presence.
Insurgents operating in Idlib and Hama provinces are mostly from rebel groups battling to topple President Bashar al-Assad. Those groups also have a foothold in Aleppo province, where Islamic State also operates.
Separately, the Syrian Observatory for Human Rights said at least 12 Islamic State fighters had been killed in a Russian air strike in Raqqa province on Thursday. The province is mostly under Islamic State control.
