On the stroke of midnight, firing stopped in suburbs around the capital and the devastated northern city of Aleppo, AFP correspondents said, after a day of intense Russian air strikes on rebel bastions across the country.
The nationwide cessation of hostilities, which does not include jihadist groups, is the first pause in a five-year civil war that has claimed 270,000 lives and displaced more than half the population.
"I can't hide the fact that I'm happy the war has stopped, even for a few minutes," 24-year-old regime soldier Abdel Rahman Issa said from a battlefield on the eastern outskirts of Damascus.
United Nations envoy Staffan de Mistura said peace talks would resume on March 7 if the truce holds and more aid is delivered -- a key sticking point in negotiations.
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He told reporters the special task force would meet in Geneva today and that a system had been created to deal with violations.
The task force, created by the 17-nation International Syria Support Group, would meet to "monitor and check" what has been happening on the ground, De Mistura said.
Moscow and Washington, co-chairs of the task force, have set up rival offices to oversee the truce along with a UN operation centre and would be first to deal with any infractions.
Calm held throughout the night in Aleppo city, where residents said they were considering taking their children to a rare visit to the park.
And the skylines around Damascus did not feature the typical plumes of smoke or sounds of shelling in the early morning, AFP correspondents said.
The Syrian Observatory for Human Rights, a Britain-based monitoring group, said it was also relatively quiet in the central provinces of Homs and Hama.
The ceasefire, brokered by the United States and Russia, which back opposing sides in the war, does not apply to the Islamic State jihadist group or Al-Qaeda-affiliated Al-Nusra Front.
An explosion killed two soldiers outside the town of Salamiyeh in Hama province, where IS is present.
Previous attempts to end the violence in Syria have failed and both Russia and the United States have warned that stopping the fighting on the ground will be difficult.
Analysts have also questioned whether the agreement can be effective given that it does not include IS or Al-Nusra Front.