The Syrian Observatory for Human Rights said Russian warplanes launched around 15 pre-dawn strikes on towns and villages in Idlib province.

The raids led to the death of one civilian in the village of Balyun -- the "first to die from an air strike" since the March ceasefire, Observatory head Rami Abdel Rahman said.

Home to around three million people, the Idlib region is Syria's last major rebel bastion after nine years of devastating civil war.

A Russian-backed government offensive between December and March displaced nearly a million people in the region.

A truce reached on March 6 has largely halted the fighting but President Bashar al-Assad has vowed to retake full control of the region.

Russia resumed air strikes earlier this month and on Monday hit parts of Idlib and neighbouring Hama provinces with dozens of air strikes, the Observatory said.

The strikes came as ground fighting left 19 government troops and 22 jihadists dead, the Britain-based monitor said.

The war in Syria has killed more than 380,000 people and displaced nearly half of the country's pre-war population since it started in 2011.