Aid agencies on Friday warned of dire humanitarian consequences if a Russia-Turkey deal to avert a regime assault on Syrias last major rebel stronghold was not fully implemented within days.
Regime ally Russia and rebel backer Turkey agreed last month to set up a buffer zone around the northwestern region of Idlib to separate jihadist and rebels inside from government fighters massing on its edges.
Under the accord, jihadists have until Monday to withdraw from the buffer zone semi-circling the region of some three million people, but have not yet shown any sign of moving.
On Friday, international aid groups working in Idlib warned that failure to implement the deal could spark renewed violence and trigger mass displacement.
Local partner organisations and "civilians receiving aid have expressed fears that violence could spiral out of control in the next few days if either the deal collapses or fighting escalates in areas not covered by it", they said.
"Even a limited military offensive would displace hundreds of thousands of people," CARE International, the International Rescue Committee (IRC), Mercy Corps and Save the Children said in a statement.
Nearly half of the people living in Idlib have fled from their homes in other parts of the war-torn country, according to the United Nations, and many already depend on aid.
"If this deal falls short and military operations start, many hundreds of thousands will struggle to get the help they will so badly need," warned Lorraine Bramwell, IRC's Syria country director.
For the agreement to be implemented, Idlib's dominant force, an alliance led by Al-Qaeda's former Syria affiliate, and other jihadists must withdraw from the planned buffer zone by Monday.
But the Hayat Tahrir al-Sham (HTS) alliance has not yet officially responded to the deal, and a Britain-based war monitor said on Friday that no jihadists had withdrawn yet from the buffer zone.
"There has been no withdrawal of any members of the jihadist factions with their light weapons," the Syrian Observatory for Human Rights monitoring group said.
An AFP correspondent said that residents in the area received warning messages Friday on their mobile phones from the Syrian army.
"Get away from the fighters. Their fate is sealed and near," one said.
"Don't allow the terrorists to take you as human shields," said another, addressed to residents of the planned buffer zone.
HTS, jihadists from the Turkestan Islamic Party and current Al-Qaeda outfit Hurras al-Deen control more than two-thirds of the expected demilitarised zone.
Turkey-backed rebels and jihadists this week met a first cut-off date on Wednesday to remove their heavy weaponry from the buffer strip.
But it is not clear what will happen if the second and last October 15 deadline is not met.
Despite progress in implementing the accord, Assad insisted on Sunday it was a "temporary measure" and that Idlib would eventually return to state control.
The Syrian war has killed more than 360,000 people since it erupted in 2011 with the brutal repression of anti-government protests.