Syrian forces have called ceasefire in Iblib

"From 00:00 on May 18, Syrian armed forces unilaterally ceased fire in the Idlib de-escalation zone," the Russian military's centre for reconciliation in Syria said in a statement.

"However, firing targeting government forces' positions and civilians in the provinces of Hama, Latakia and Aleppo continues," it added.

The statement came after Britain, France, the United States and eight other countries at the UN Security Council warned on May 10 of a potential humanitarian catastrophe from an all-out assault in Idlib region, in a statement opposed by Russia.

Western powers are concerned that the Russia-backed Syrian government will launch a full-scale assault, despite a deal reached with Turkey, who back rebel forces, to set up a de-escalation zone in Idlib.

Meanwhile three civilians were killed and others injured on Sunday as a result of artillery shelling from the Syrian regime forces and their loyalist militia on the town of Khan Sheikun, south of Idlib, northwest of Syria.

A source from Syria's civil defense (the White Helmets) told The New Arab that the forces of the regime and the militias supporting them based in the countryside Hama bombed the city of Khan Sheikun several artillery shells, killing three brothers and wounding other civilians.

The Syrian Observatory for Human Rights, however, said that shelling by the regime's forces had continued on Sunday, despite the announcement by the Russian army.

The Syrian state agency Sana said rockets and mortar shells were fired at the northern part of Hama province by "terrorist groups", using the regime's terminology for jihadists and rebels.

It added that the army responded with fire that destroyed positions held by Syria's former Al-Qaeda affiliate Hayat Tahrir al-Sham (HTS).

The group controls most of Idlib province as well as parts of neighbouring Aleppo, Hama and Latakia provinces.

Syrian forces and their Russian allies have stepped up air strikes and shelling in the rebel-controlled Idlib region since late April, raising alarm over a possible looming full-on offensive by Damascus to seize the territory. 

About three million people live in Idlib, the largest area still outside the control of the Syrian government.     

Syria's war has killed more than 370,000 people and displaced millions inside Syria and abroad since starting in March 2011 with a crackdown on anti-government demonstrations.