BEIRUT: Air strikes killed 19 people in a village in Syria's rebel stronghold of Idlib overnight, a rescue service and the Syrian Observatory for Human Rights said on Wednesday.

The Observatory, a Britain-based war monitoring group, said Syrian government or Russian aircraft struck the village. There was no immediate comment from the Syrian military or Russia, which have both repeatedly said they only target militants.

The strikes pounded the town of Maar Shureen in the northwestern province of Idlib and the dead included seven children, the Observatory said.

Idlib's civil defence, a rescue service known as the White Helmets which operates in rebel territory, said fierce bombing after midnight killed 19 people.

The Observatory said 25 others had been injured.

Government forces and their allies stepped up air strikes against opposition towns in the Hama countryside, near the southern part of Idlib, rebels said last week.

The Damascus government lost Idlib after insurgents took over the provincial capital in 2015. It has since become the only province fully under opposition control, and the most populated insurgent-held part of Syria.

Hayat Tahrir al Sham, an Islamist alliance spearheaded by the former al-Qaeda affiliate in Syria, is the dominant rebel force in Idlib. This has raised fears among civilians and Free Syrian Army rebels that the province could come under attack and turn into a major battlefield.

Thousands of civilians and fighters have poured into Idlib in the past year, bussed out of towns and cities which Syrian troops seized with the help of Russia and Iran-backed militias.

The province, bordering Turkey, is part of Russian-brokered de-escalation agreements that seek to shore up ceasefires in parts of western Syria.

Turkey, which had long backed some Syrian rebel factions, set up observation posts in Idlib in October under a deal with Russia and Iran to reduce fighting there.

Turkish President Tayyip Erdogan has said the Idlib military operation in Idlib was largely completed. The deployment was also seen partly aimed at containing Kurdish influence nearby in northern Syria.