Five of the victims died in the village of Al-Malaja in southern Idlib province while the other four were killed in raids on the town of Saraqeb in the east, according to the Syrian Observatory for Human Rights.

A number of people were wounded, some seriously, the monitor's head Rami Abdel Rahman told AFP, though he was unable to say how many.

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

The Hayat Tahrir al-Sham jihadist alliance also controls parts of neighbouring Aleppo and Latakia provinces.

The region is one of the last holdouts of opposition to forces of Syrian President Bashar al-Assad.

A ceasefire announced by Russia has largely held since late August.

But the Observatory says 48 civilians -- including 16 children -- have been killed in Russian air strikes on the region since the start of November.

The Britain-based monitor, which relies on sources inside Syria, says it determines who carries out an air strike according to flight patterns, as well as aircraft and the munitions involved.

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

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