DAMASCUS: Guns fell silent across Syria on Saturday after a landmark United Nations-backed ceasefire came into effect, as a special task force led by rivals Moscow and Washington prepared to begin monitoring the fledgling truce.

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.

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.

The nationwide cessation of hostilities is the first pause in five years of a civil war that has claimed more than 270,000 lives.

"I can't hide the fact that I'm happy the war has stopped, even for a few minutes," 24-year-old Syrian army soldier Abdel Rahman Issa said from a battlefield on the eastern outskirts of Damascus.

"If it continues like this, maybe we can go home."

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

Fighting appears to have "calmed down", he told reporters shortly after midnight, adding that a special task force would meet in Geneva on Saturday to monitor the ceasefire.

Moscow and Washington, co-chairs of the task force which back opposing sides in Syria, have set up rival monitoring offices along with the UN operation centre, and would be first to deal with any infractions.

"The important point... is if (any) incidents will be quickly brought under control and contained," de Mistura said, adding that "a military response should be... the last resort".

Previous attempts to end the violence in Syria have failed and both Russia and the US have warned that stopping fighting on the ground will be difficult.

Some scepticism

Analysts have also questioned whether the ceasefire can be effective on Syria's complex battlefields, as it does not include fighters from the militant Islamic State (IS) group and Al Nusra Front.

Intermittent clashes between Syrian forces and both groups continued after midnight, the Observatory said, as well as fighting between militants and Kurdish forces.

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

US Ambassador Samantha Power acknowledged there was "some scepticism" as to whether the ceasefire would last, but said it offered the "best chance to reduce the violence".

A spokesman for Turkey's presidency expressed worries over the ceasefire "because of the continuing Russian air raids and ground attacks by forces of [President Bashar al-] Assad".

Russia began air strikes in Syria in September saying it was targeting "terrorists", but critics have accused Moscow of hitting rebel forces in support of the Syrian government.

Deputy Foreign Minister Gennady Gatilov said the agreement could be "a turning point" in the war, even as Russian planes launched a wave of attacks on non-jihadist rebel areas.

The Observatory reported Russian strikes Friday on rebel bastions including the Eastern Ghouta region outside Damascus, northern Homs province and the west of Aleppo province.

The head of the Britain-based monitor, Rami Abdel Rahman, said at least 40 members of the Syrian forces were killed battling rebels in northern Latakia province.

'No other way'

Russian President Vladimir Putin insisted Moscow would continue targeting “terrorist groups”.

“The decisive fight against them will, without doubt, be continued,” he said in televised remarks. “There is no other way.“

Moscow backs Assad and Washington supports the opposition, but both have made a concerted push for the ceasefire to be respected.

Speaking in Washington on Thursday, President Barack Obama put the onus firmly on the regime and Russia, saying the “world will be watching” whether they keep to the truce.

US State Department spokesman Mark Toner said Washington had received assurances from Moscow that it would not bomb the “moderate opposition” after the truce.

“I don't know how to put it any better than saying: 'It's put up or shut up time,'” he told reporters. Iran, another key Assad ally, has said it is confident the regime will abide by the agreement.

But rebel groups on the ground have been less optimistic, and Al Nusra's chief Mohammad al-Jolani on Friday urged regime opponents to intensify their attacks.

“Negotiations are the ones conducted on the battlefield,” he said in an audio message.

Syria's top opposition grouping, the High Negotiations Committee (HNC), said Friday that 97 opposition factions had agreed “to respect a temporary truce”, but only for an initial two weeks.

It said Damascus and its allies must not continue attacking rebel forces “under the pretext of fighting terrorism”.