Russia has called for a long-term ceasefire in the northern Syrian city of Aleppo, hours after declaring a two-day pause in the fighting there.
The Russian defence ministry said the "regime of calm", which went into effect at midnight, was an effort to stabilise the situation in Aleppo.
Hundreds of people have been killed in the divided city in recent months.
Russian air strikes have supported an attempt by Syrian government forces to encircle rebel-held western areas.
On Wednesday, the US said the government's offensive was violating a nationwide cessation of hostilities brokered by the US and Russia in February.
The Russian defence ministry statement issued late on Wednesday said the regime of calm had been introduced in Aleppo "with the goal of lowering the level of armed violence and stabilising the situation".
The ministry did not say if any other parties to the conflict had been consulted.
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But it accused the jihadist group al-Nusra Front, an al-Qaeda affiliate that is excluded from the cessation of hostilities, of attacking government-controlled districts of Aleppo with frequent rocket launchers and mortars.
The ministry also said al-Nusra fighters and allied rebels had launched assaults on government forces in two villages south-west of Aleppo, where dozens of combatants were reportedly killed in fierce clashes on Tuesday.
The announcement of the Aleppo truce came shortly after US Secretary of State John Kerry warned that the truce was "frayed and at risk", mainly because of violations by government forces.
"Russia needs to understand that our patience is not infinite, in fact it is very limited," he said.
"We have made it very clear that unless we get a better definition of how this cessation is going to work (...) we are not going to sit there while Assad continues to assault Aleppo and while Russia continues to support that effort."
Speaking to reporters in St Petersburg on Thursday morning, Russian Deputy Foreign Minister Mikhail Bogdanov was asked if the Aleppo truce could become a long-term ceasefire.
"We call for this," he was quoted as saying by Russia's Tass news agency.
Mr Bogdanov also urged Syrian government and opposition representatives to resume UN-brokered peace talks in Geneva, which broke down in April as the fighting around Aleppo escalated.
"Those who sought a political settlement should promptly resume the intra-Syrian dialog, too," he said.
The humanitarian organisation Mercy Corps meanwhile warned that aid had been cut from rebel-held areas of Aleppo, where between 200,000 and 300,000 people are still thought to live, for the longest period since fighting erupted in the city in 2012, driving up food prices.
