A ceasefire brokered by Russia and the United States took effect in Syria at sundown on Monday, despite scepticism over how long the truce in the five-year conflict would hold.
The initial 48-hour truce came into force at 7:00 pm local time (1600 GMT) across Syria except in areas held by jihadists like the Islamic State group.
AFP correspondents in Syria's devastated second city Aleppo, divided between a rebel-held east and regime-controlled west since mid-2012, said fighting appeared to have stopped as the ceasefire took effect.
A final rocket was fired from the east into government areas just five minutes before 7:00 pm, while rebel neighbourhoods had not been hit by bombardments for about two hours, they said.
The Syrian Observatory for Human Rights monitoring group said it was "quiet" on nearly all fronts.
"I was checking the time all day, waiting for it to turn 7:00," said Khaled al-Muraweh, a 38-year-old shopkeeper in the Furqan district of western Aleppo.
More From This Section
"I hope the ceasefire holds so I can see my brother who lives in the opposition-held part of the city," added al-Muraweh.
In Aleppo's east, residents roamed the streets to celebrate the start of the Muslim holiday of Eid al-Adha.
"This was the calmest day since I got married a week ago," said Shadi Saber, 26, as he waited for a shave at the barber shop.
Syria's armed forces immediately announced a seven-day "freeze" on military operations, but opposition forces have yet to formally sign on.
The deal's fragility was underscored just hours before sundown when President Bashar al-Assad vowed to retake the whole country from "terrorists".
The agreement, announced Friday after marathon talks between Russia and the US, has been billed as the best chance yet to halt Syria's five-year war, which has left 290,000 people dead.
Under the deal, fighting will halt across areas not held by jihadists and aid deliveries to besieged areas will begin, with government and rebel forces ensuring unimpeded humanitarian access to Aleppo in particular.
Rebels broke a regime siege of the east in August but Assad loyalists restored the blockade on September 8.
The ceasefire will be renewed every 48 hours and, if it holds for a week, Moscow and Washington will begin unprecedented joint targeting of jihadist forces.
Many in the Pentagon are deeply uneasy about the proposed collaboration, with one defence official saying "the proof will be in the pudding".