Russian president Vladimir Putin on Wednesday called for "compromise and concessions" from all parties to end Syria's six-year civil war as he opened a key summit with the leaders of Turkey and Iran in the Black Sea resort of Sochi.

"It is obvious that the reform process will not be simple, it will require compromise and concessions from all parties, including obviously the Syrian government," Putin said.  

"I count on the fact that Russia, Iran and Turkey will put in their best efforts to make this work as productive as possible," he added.