Turkish Foreign Minister Mevlut Cavusoglu met his Russian counterpart Sergei Lavrov ahead of the four-way summit on Syria to be held in Istanbul on Saturday, private broadcaster CNN Turk said, without providing any details.

Russia's Vladimir Putin, Germany's Angela Merkel, France's Emmanuel Macron and Turkey's Tayyip Erdogan are due to meet in Istanbul later to discuss the latest developments in Syria's rebel-held Idlib province and the political process for the resolution of the conflict.