Russian forces carried out air strikes in Idlib, a de-escalation zone in northwestern Syria, killing at least five civilians, local sources said on Monday.

According to the Syrian opposition aircraft observatory, Russian warplanes targeted the rural areas of the northwestern Aleppo province in the morning.

The attack killed at least five people and injuring nine others, said the White Helmets, a local civil defense agency.

Turkey has pushed hard for a cease-fire in Idlib after the region endured months of battering by forces loyal to the Bashar al-Assad regime and its allies, sending about a million civilian refugees flocking towards the Turkish border.

Turkey and Russia agreed in September 2018 to turn Idlib into a de-escalation zone in which acts of aggression are expressly prohibited.

Since then, more than 1,300 civilians there have been killed in attacks by the regime and Russian forces as the cease-fire continued to be violated.

Over one million Syrians have moved near the Turkish border due to intense attacks over the last year.