Russia and Turkey have agreed to a cease-fire in Syria’s northwestern Idlib province, the last rebel stronghold in Syria, after fighting there escalated over the past several months and threatened to bring the two countries into direct confrontation.

President Recep Tayyip Erdogan of Turkey, which supports opposition forces in Syria, and President Vladimir Putin of Russia, which supports the Syrian government, met for six hours in Moscow to reach the cease-fire deal, which was to begin at midnight Thursday night.

The agreement included setting up a nearly four-mile security corridor along a key east-west highway, which Turkey and Russia will hold joint patrols around beginning later this month. Erdogan said Putin also agreed to have Russia help the close to one million displaced Syrian refugees on the border with Turkey return to their homes.

Putin said he hoped the deal would be a “good basis for ending the fighting in the Idlib de-escalation zone, put an end to suffering of civilian population and contain a growing humanitarian crisis.”

However, fighting appeared to continue past the cease-fire deal, as Turkish state media reported that Turkish forces on Thursday killed 21 Syrian troops and destroyed military equipment after two Turkish soldiers were killed earlier in the day.

More than 300 civilians, at least a third of whom were children, have been killed in Idlib since December.