A cessation of hostilities in Syria has come into effect under a ceasefire warring sides in the five-year conflict have committed to.

A monitoring group said fighting appeared to have stopped across most of western Syria, with isolated incidents of fire in some areas.

However late yesterday a car bomb killed two people at the entrance of a town in the province of Hama,

Damascus and its ally, Russia, as well as 97 insurgent groups fighting against them, had said they would commit to the plan.

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The truce does not apply to Islamic State (Isis) and al-Qaeda affiliate the Nusra Front, and the Syrian Government and Moscow have said they will not halt combat against those militants.

Fighting had raged across much of western Syria right up to when the agreement went into effect, the Britain-based Syrian Observatory for Human Rights said. Shortly after midnight on Friday, there was calm in many parts of the country.

"In Damascus and its countryside ... for the first time in years, calm prevails," Observatory director Rami Abdulrahman said.

"In Latakia, calm, and at the Hmeimim air base there is no plane activity," he said, referring to the base Russia's warplanes operate from.

On Friday at least 40 government soldiers and allied fighters, and 18 insurgents were killed in battles and air strikes in Latakia province, the Observatory reported.

Also in the hours before the halt, six people died in an air raid in western Aleppo province, it said. As well, rescue workers said at least five people were killed in Douma, near Damascus.

Syrian boys play soccer between destroyed buildings in the old city of Homs, Syria. Photo / AP
Syrian boys play soccer between destroyed buildings in the old city of Homs, Syria. Photo / AP

Nusra Front on Friday called for an escalation in fighting, urging insurgents to intensify their attacks in a call that added to the dangers facing the fragile agreement.

Under the measure, which has not been signed by the Syrian warring parties themselves and is less binding than a formal ceasefire, the Government and its enemies were expected to stop shooting so aid could reach civilians and peace talks could begin.

Aid has been delivered to some areas this year in a series of localised agreements, but the United Nations demands unhindered access to all Syrians in need of help.

UN Syria envoy Staffan de Mistura intends to reconvene talks on March 7 provided the halt in fighting largely holds.

- AAP