A ceasefire brokered by Russia and Turkey has come into effect in the northwest Syrian province of Idlib.
The deal was signed in Moscow on Thursday by Russian President Vladimir Putin and his Turkish counterpart, Recep Tayyip Erdogan.
A monitoring group, the Syrian Observatory for Human Rights, said a relative calm descended on the region.
It comes after weeks of intense fighting between Turkish-backed rebels and Syrian forces supported by Russia.
Around 60 Turkish soldiers have been killed during a Syrian government offensive on Idlib - the last area of the country held by anti-government forces.
The fighting has led to a humanitarian crisis in the province, and sparked fears of a direct military conflict between Russia and Turkey, a Nato member.
Before the truce came into effect, Turkey said two of its soldiers had been killed in clashes with Syrian President Bashar al-Assad's forces.
Turkey said it had killed 21 Syrian troops and destroyed artillery pieces.
What is the ceasefire deal?
The agreement was announced after six hours of talks between Mr Putin and Mr Erdogan in the Russian capital.
The two sides said the deal included:
- A ceasefire from 00:01 local time on Friday (22:01 GMT Thursday) on the whole line of contact
- A security corridor 6km (four miles) north and 6km south of Idlib's key M4 motorway, which connects the government-held cities of Aleppo and Latakia
- Joint Russian-Turkish patrols along the M4 from 15 March
During the talks, President Erdogan failed to obtain a withdrawal by government forces from their recent territorial gains.
The agreement also lacked any mention of a safe zone where displaced Syrians could take shelter. The UN estimates that nearly a million people have been uprooted by the offensive - the largest exodus of the entire nine-year war.
President Assad has pledged to recapture "every inch" of Syrian territory, and regaining control of major highways in Idlib would be a boost to Syria's sanctions-hit economy.
But Mr Assad's forces depend heavily on support from Russia and militias backed by Iran.
Speaking on Russian news outlet Russia 24, Mr Assad said that, in the long run, he wanted to normalise relations with Turkey again, despite the conflict.
"For us and for [Russia], Turkey is a neighbour state, it would be natural to have normal relations with a neighbour state," he added.
There have been several ceasefires over Idlib in the past. In September 2018, Mr Putin and Mr Erdogan agreed to establish a "de-escalation zone." The zone was intended to act as buffer between the two sides, with clear lines of control, but the ceasefire collapsed.
After the latest agreement was reached, Mr Putin told reporters that it would "serve as a good basis for ending fighting". But Mr Erdogan added that Turkey reserved the right to "retaliate with all its strength against any attack" by Damascus.
The BBC's diplomatic correspondent Jonathan Marcus says fundamental questions remain about the ceasefire, including how long the truce will last, whether Syrian government forces or Turkish troops will pull back to designated zones, and what will be the fate of the huge number of refugees.
In short, our correspondent says it is unclear whether the Assad regime and its Russian backers have given up on the idea of seizing back all of Idlib, and whether this is a permanent policy shift or just a temporary expedient to reduce the current tensions with Ankara.