On the stroke of midnight, firing stopped in suburbs around the capital and the devastated northern city of Aleppo, media correspondents said, after a day of intense Russian air strikes on rebel bastions across the country.

Monitoring group the Syrian Observatory for Human Rights said it was quiet in the north of Latakia province and in the central provinces of Homs and Hama.

"I may be up late tonight and hope I won't be wakened tomorrow by the sound of airplanes," Mohammed Nohad, a resident of Aleppo's southern rebel-held district of Al-Kalasseh, told media.

The nationwide cessation of hostilities would be the first pause in fighting since Syria's civil war broke out in 2011.

UN envoy Staffan de Mistura said peace talks would resume on March 7 if the ceasefire agreement holds and more aid is delivered -- a key sticking point in negotiations for a truce.

Fighting appears to have "calmed down", although one incident is being investigated, and a special task force will meet today to monitor the fledgling ceasefire, he told reporters in Geneva.

Previous attempts to end the fighting have failed and Russia and the US, which back opposing sides in the fight, have warned that applying it on the ground will be difficult.

Analysts have also questioned whether it can be effective on Syria's complex battlefields, as the truce does not include jihadists from the Islamic State group and Al-Nusra Front.

Intermittent clashes between pro-regime forces and both groups continued after the ceasefire began, the Observatory said, as well as fighting between jihadists and Kurdish forces.

Less than an hour before the ceasefire, the UN Security Council gave its unanimous backing to the truce in a resolution drafted by the US and Russia.

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