Meeting in Istanbul on Saturday, leaders of Turkey, Russia, Germany and France will discuss ways to achieve a “permanent cease-fire” in Idlib, Syria, according to Chancellor Angela Merkel’s spokesman.

“The Turkey-Russia agreement on a demilitarized zone in Idlib has been an important first step to prevent a large-scale military assault and a humanitarian catastrophe there,” Steffen Seibert said in a video message posted on Twitter.

“And now the question will be how to move from there to a permanent cease-fire in Idlib, achieve permanent security for the people of Idlib,” he stressed.

Turkey and Russia agreed on Sept. 17 to establish a demilitarized zone in Syria's northwestern province of Idlib.

Under the deal, opposition groups in Idlib are to remain in areas where they are already present, while Russia and Turkey carry out joint patrols in the area with a view to preventing a resumption of fighting.

Turkish President Recep Tayyip Erdogan is hosting the four-nation summit, with the participation of Merkel as well as Russian President Vladimir Putin and French President Emmanuel Macron.

Staffan de Mistura, the UN special Syria envoy, will also attend the summit.