Eight others were wounded in the raids and some of them are in a "critical" condition, said Rami Abdel Rahman, the head of the Britain-based Syrian Observatory for Human Rights war monitor.

The air strikes -- the third wave by Russian aircraft in eight days on northwestern Syria -- struck the village of Kafr Ruma in the jihadist-run enclave of Idlib, the Observatory said.

The Idlib region, which is home to some three million people including many displaced by Syria's eight-year civil war, is controlled by the country's former Al-Qaeda affiliate.

Syrian President Bashar al-Assad's forces launched a blistering military campaign against Idlib in April, killing around 1,000 civilians and displacing more than 400,000 people from their homes.

A ceasefire announced by Russia has largely held since late August, although the Observatory says dozens of civilians have been killed in sporadic bombardment since then.

Last month Assad said Idlib was standing in the way of an end to the civil war that has ravaged his country through most of the current decade.

Syria's war has killed 370,000 people and displaced millions from their homes since beginning in 2011 with the brutal repression of anti-Assad protests.