The UN on Tuesday welcomed a Turkish-Russian agreement to establish a demilitarized zone in Syria’s northwestern Idlib province.

The two countries agreed Monday to establish a demilitarized zone in Idlib, Syria’s last opposition stronghold, after a meeting in Sochi between Turkish President Recep Tayyip Erdogan and Russian, counterpart Vladimir Putin.

The agreement "should avert a full-scale military operation and provide reprieve for millions of civilians," said Stephane Dujarric, spokesman for the Secretary-General Antonio Guterres, in a statement.

Guterres urged all parties in Syria to cooperate in implementing the agreement and ensure safe and unimpeded humanitarian access in all areas.

"The Secretary-General stresses the need for swift action to address the root causes of the conflict and forge, at long last, a durable political solution in line with UN Security Council resolution 2254," read the statement.

Ankara and Moscow also signed a memorandum of understanding calling for the “stabilization” of Idlib's de-escalation zone, in which acts of aggression are expressly prohibited.

According to the MoU, opposition groups in Idlib will remain in areas in which they are already present, while Russia and Turkey will conduct joint patrols in the area with a view to preventing renewed fighting.

Syria has only just begun to emerge from a devastating conflict that began in 2011 when the Assad regime cracked down on demonstrators with unexpected ferocity.