AMMAN/ISTANBUL (REUTERS) - Syria's war-battered Idlib region was quiet but tense on Friday (March 6) as a ceasefire deal between Moscow and Ankara took effect, with residents and opposition forces describing a lull in air raids that have pounded the last rebel-held enclave in Syria.

Russia and Turkey made the agreement on Thursday evening, after six hours of talks in Moscow, to contain a conflict that has displaced nearly a million people in three months in north-west Syria.

Russia and Nato-member Turkey back opposing sides in Syria's nine-year-old war. Moscow supports President Bashar al-Assad and Turkey backs some rebel groups, and the two sides had been edging closer to direct confrontation in recent weeks.

Several previous deals to end the fighting in Idlib have collapsed. Analysts and residents said they feared the latest ceasefire would also fizzle out, as it did not address the humanitarian crisis or air protection in any detail.

"This deal isn't designed to last, rather it is designed to fail - and I am afraid in the not too distant future," said Mr Galip Dalay, IPC-Mercator fellow at the German Institute for International and Security Affairs.

"Any ceasefire arrangement in Idlib, unless it has a no-fly zone dimension, is bound to fail. Deals in the past never de-escalated. They merely froze the crisis until the next escalation."

Arriving for a meeting of European Union foreign ministers in Zagreb, Dutch minister Stef Blok said the ceasefire deal should be cemented with a no-fly zone to stop any further bombing of hospitals.

HUMANITARIAN CRISIS

The latest offensive in Idlib by Mr Assad's forces, backed by Russian air strikes, sparked what the United Nations says may be the worst humanitarian crisis yet in a war that has driven millions from their homes and killed hundreds of thousands.

Russia had repeatedly played down any talk of a refugee crisis and accused Turkey of violating international law by pouring troops and equipment into Idlib since early last month.

About 60 Turkish troops have been killed in that time.

Turkey, which has the second-largest army in the transatlantic Nato alliance, has tried to resist the Syrian government advance and prevent a wave of refugees over its southern border. It already hosts 3.6 million Syrian refugees.

The ceasefire deal establishes a security corridor on each side of Idlib's key east-west M4 highway, along which joint Russian-Turkish patrols will begin on March 15. The corridor stretches 6km to the north and 6km to the south of the M4 - effectively advancing Russia's presence further north into Idlib. Details of its operation are due to be agreed in the next week.

Russian President Vladimir Putin, standing next to his Turkish counterpart Recep Tayyip Erdogan, said on Thursday he hoped the deal "will serve as a good basis for a cessation of military activity in the Idlib de-escalation zone".

Mr Erdogan said the sides would work together to supply aid to Syrians in need, but that Turkey retained the right to "respond to all (Syrian) regime attacks in the field". Residents and fighters in the region said the main front lines - which have seen heavy air strikes by Russian and Syrian jets, and intense Turkish artillery and drone strikes on Mr Assad's forces - were quiet hours after the ceasefire came into effect at midnight.

'VERY TENSE CALM'

There was only sporadic fire from machine guns, mortars and artillery by Syrian government forces and Iranian militias on some front lines in the south of Idlib and also in the adjacent Aleppo province, they said.

"In the first hours, we are witnessing a very tense calm from all warring parties," said Mr Ibrahim al-Idlibi, an opposition figure in touch with rebel groups on the ground.

"Everyone is aware that violations by any side would be met with a response. But this a very fragile truce."

The Syrian Observatory for Human Rights monitoring group reported that the first eight hours of the ceasefire had passed with "relative calm", and the skies had been free of Syrian government and Russian warplanes.

As the ceasefire was being negotiated on Thursday, Turkey staged an attack with a combat drone against Mr Assad's forces and "neutralised" 21 Syrian government soldiers, a term commonly used to mean killed, the Turkish Defence Ministry said. Earlier, two Turkish troops were killed by the Syrian side.

Syrian state media did not report the latest ceasefire deal.

In particular, it did not address a Turkish demand that Syrian forces withdraw to the edge of a buffer zone agreed in Sochi in 2018.

It also did not detail a "safe zone" or describe how displaced people could return to the homes they have fled to escape the Russian-backed offensive.

"No one has mentioned a safe zone or areas of withdrawal.

"There is no pullout, and where will the displaced go (who) would never accept going to (Assad) regime areas? What we have heard is not comforting," said Mr Ahmad Rahhal, a former general in the Syrian government forces who defected to the opposition.

UN Nations Secretary-General Antonio Guterres said he hoped the deal would lead to "an immediate and lasting cessation of hostilities that ensures the protection of civilians in north-west Syria, who have already endured enormous suffering", UN spokesman Stephane Dujarric said in a statement.