A cessation of hostilities in Syria came into effect at the agreed time of midnight on Saturday, under a U.S.-Russian plan which warring sides in the five-year conflict have said they would commit to.
A monitoring group said shortly after midnight that across most of western Syria fighting appeared to have stopped, with isolated incidents of fire in some areas. On Saturday morning, a car bomb went off in at the entrance of a town in the Syrian province of Hama, killing at least two, according to state TV.
The truce does not apply to Islamic State and Al Qaida 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 until the agreement came into effect, the Britain-based Syrian Observatory for Human Rights said.
Shortly after midnight, there was calm in many parts of the country, it said.
"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 in reference to the Latakia base where Russia's warplanes operate from.
In the northern city of Aleppo some gunfire had been heard shortly after midnight, and there were some blasts heard in northern Homs province, but it was not clear what had caused them, he said.
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. Near Damascus, dozens of air raids hit besieged Daraya suburb. Rescue workers said at least five people were killed in Douma northeast of the capital.
UN appeal for peace talks
Nusra Front on Friday called for an escalation in fighting, urging insurgents to intensify their attacks against Assad and his allies 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 are expected to stop shooting so aid can reach civilians and peace talks begin.
Aid has been delivered to some besieged areas of the country this year in a series of localized agreements, but the United Nations demands unhindered access to all Syrians in need of help.
Peace talks collapsed earlier this month before they began, and Damascus and Moscow intensified assaults in the north and northwest of the country.
UN Syria envoy Staffan de Mistura said late on Friday he intends to reconvene peace talks on March 7 provided the halt in fighting largely holds.
The Syrian government has agreed to the cessation plan, but says it could fail if foreign states supply rebels with weapons or insurgents use the truce to rearm.
The main Saudi-backed opposition alliance, which has deep reservations, said it would accept it for two weeks but feared the government and its allies would use it to attack opposition factions under the pretext that they were terrorists.
The U.S.-backed Kurdish YPG militia, which is battling Islamic State in the northeast and Turkish-backed rebel groups in the northwest, said it would abide by the U.S.-Russian plan, but reserves the right to respond if attacked.
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