ASTANA, May 4 (Xinhua) -- Russia, Iran and Turkey signed a memorandum on the creation of four safe zones in war-torn Syria here on Thursday.

"The ceasefire guarantor states announce that the memorandum on the establishment of de-escalation zones in Syria provide the creation of security zones to stop violence, improve humanitarian situation and create conditions for the advancement of the process and political settlement of the Syrian conflict," Kazakh Foreign Minister Kairat Abdrakhmanov said.

The four safe zones would be in the provinces of Idlib and Homs, in eastern Ghouta, and in the south, where fighting between the Syrian government forces and the rebels would stop, and flights halted

The aim is to "put an immediate end to the violence," "provide the conditions for the safe, voluntary return of refugees," and allow immediate delivery of humanitarian aid, the memorandum said.

UN Special Envoy for Syria Staffan de Mistura hailed the plan. "Today in Astana I think we have been able to witness an important promising positive step in the right direction in the process of de-escalation of the conflict," he said.

The Syrian government supported the plan, but Syrian opposition announced it would not accept it, saying the pact threatens Syria's territorial integrity.

Russia and Iran have been backing Syrian President Bashar Assad, while Turkey backs Syrian rebels. The six-year war in Syria has cost over 320,000 lives.