Russian jets carried out air strikes on areas in western Syria on Saturday and an Islamic State stronghold in the north was rocked by a large explosion, the Syrian Observatory for Human Rights monitoring group said.
Russia, a top ally of Syrian President Bashar al-Assad, started bombing in Syria on Sept. 30 saying it was targeting Islamic State militants, a campaign that has drawn Moscow deeper into Syria's more than four-year conflict.
Rebels on the ground and Western states have said Moscow's air campaign, which has been combined with ground attacks by pro-government forces, have mainly targeted rebel groups not associated with Islamic State, including U.S.-trained fighters.
Russian strikes hit northern areas of Latakia province, the coastal heartland of Assad's Alawite minority sect, as well as northern areas of Hama province further east, the Syrian Observatory for Human Rights said.
There was no immediate information on casualties.
The Observatory says Islamic State has no real presence in these areas. However, there were other militants in northern Syria, such as Chechens, that Russia might want to take out.
Syrian state television said in a newsflash that attacks carried out by government forces in the area had killed and wounded a number of "terrorists", a term it uses to describe all insurgents in Syria.
The Observatory said a large explosion hit a building on the outskirts of the town of al-Bab in northern Syria, which is held by the ultra-hardline Islamic State.
It was not immediately clear what caused the blast in the building, which Islamic State had used to store explosives, according to the Britain-based Observatory, which tracks the conflict using sources on the ground.
On Friday, Islamic State insurgents seized villages in the same province from rival insurgents, in battles close to the city of Aleppo.
Human Rights Watch said late on Friday that the first Russian air strikes on northern Homs last month killed at least 17 civilians and should be investigated for possible violations of the laws of war.
Russian President Vladmir Putin said earlier this month that reports of civilian deaths in Russian air strikes on Syria were an "information attack".