Russia and its allies halted airstrikes in Syria’s Idlib region on Sunday as a cease-fire agreed with Turkey came into force, residents, rebels and respondents said, although few were optimistic the truce would hold.

Hundreds of thousands of people have fled Idlib province in recent weeks as Russian jets and Syrian artillery pounded towns and villages in a renewed government assault aimed at clearing the opposition from its last bastion in the northwest of the country.

Turkey’s defense ministry said it was closely following cease-fire agreements in Idlib on Sunday, adding that the situation was calm “except for one or two separate incidents.”

Turkey, which for years has backed Syrian rebels fighting to oust President Bashar Assad, said on Friday it had agreed the cease-fire with Russia to stem the flow of tens of thousands of civilians uprooted by the violence.

The latest offensive had brought the Russian-led military campaign closer to heavily crowded parts of Idlib province, where nearly 3 million people are trapped, the vast majority women and children, according to the United Nations.

Senior U.N. officials said this month that the humanitarian situation had become more acute with at least 300,000 civilians now on the run in Idlib, adding to the more than half a million people who fled earlier bouts of fighting to the safety of camps near the Turkish border.

Moscow says its forces, along with the Syrian army and Iranian-backed militias fighting alongside them, are fending off terror attacks by al-Qaida militants whom they say hit populated, government-held areas.

However, they accuse the rebels of wrecking a “de-escalation zone” brokered two-years ago between Turkey and Russia.

The Syrian army said on Sunday that insurgent rockets had killed two people during shelling of residential areas in Aleppo city. Rebels and witnesses said that at least a dozen towns were hit by artillery bombing from army posts.

“Aerial bombing stopped but many towns and villages continued to be targeted by artillery rounds,” Mohamad Rashid, an activist said.

Rebels said pro-government forces were massing on the front lines and army helicopters had dropped leaflets calling on civilians to surrender and evacuate rebel-held areas.

“There is no return to the decision to cleanse all areas of the terrorist killers so join your army in achieving victory,” said a pamphlet dropped on rebel-held areas.

Past truces have proved short lived in the months-long bloody campaign to wrest control of the last rebel stronghold that has killed hundreds and left dozens of towns and villages in ruins.

On the eve of the cease-fire, at least seventeen people, mostly women and children, were killed in Syrian and Russian bombing of four main towns in Idlib province on Saturday, residents and rescuers said.