The truce brokered by Russia and the United States saw guns fall silent at sundown yesterday, with the next anticipated step being urgent relief deliveries to desperate civilians.
In second city Aleppo - a key battleground in recent weeks - AFP correspondents in both the rebel-held east and the government-held west reported the night had passed without air strikes or rocket fire.
Residents remained out on the streets until midnight, taking advantage of the lull in fighting to celebrate the first day of the Muslim Eid al-Adha holiday.
Britain-based monitoring group the Syrian Observatory for Human Rights said the main battlefronts were "completely calm".
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US Secretary of State John Kerry told reporters in Washington it was "far too early to draw conclusions" about the success of the ceasefire but urged all sides to seize the opportunity.
"For all the doubts that remain, and there will be challenges in the days to come, this plan has a chance to work," he said of the deal he agreed on Friday with his Russian counterpart Sergei Lavrov.
In the opposition-held central town of Talbisseh, which came under heavy fire in the run-up to the truce, activist Hassaan Abu Nuh said the regime bombardment had stopped.
"We usually stay up all night with the airplanes, but thank God last night we could all sleep," he told AFP.
In the largely rebel-held northwestern province of Idlib, where air strikes killed 13 people yesterday, an activist reported a quiet night too.
"This time, we were able to sleep well. Last night was amazing," Nayef Mustafa told AFP from the town of Salqin.
"People are only expecting it to stay calm for the (Eid) holiday," he said.