Russia, Iran and Turkey have agreed to deploy observers on the edge of a de-escalation zone in northern Syria's Idlib region, which is largely controlled by Islamist militants, Turkey's foreign ministry said on Friday.
"Observers from these three countries will be deployed at check and observation points in safe zones that form the borders of the de-escalation zone," the ministry said in a statement after talks in Kazakhstan.
It said the mission of the observers would be to prevent clashes between "the (Syrian) regime and the opposition forces, and any violations of the truce".
Idlib province, in northwest Syria on the border with Turkey, is largely under the control of a rebel alliance spearheaded by the former al Qaeda offshoot Nusra Front.
It was one of four regions across Syria, mainly controlled by opponents of President Bashar al-Assad, which Russia, Iran and Turkey agreed in May to designate as de-escalation zones in support of a ceasefire agreement.
Russia and Iran have been strong supporters of Assad during the six-year-old conflict, while Turkey has backed some of the rebel factions who fought to overthrow him.
"This announcement of a de-escalation zone in Idlib constitutes the final stage of the realization of the memorandum signed in May," the Turkish foreign ministry said, adding that the May accord had brought a significant decline in violence.
"With this latest development, the memorandum is making a significant contribution to providing necessary conditions to further the political solution process going on in Geneva under UN monitoring."