The death toll from purported Russian airstrikes on the Islamic State-held Syrian city of Raqqa has climbed to at least 55, mostly civilians.
The extremist group has controlled the city in northern Syria since 2013 and considers it the capital of its self-styled caliphate.
The Britain-based Syrian Observatory for Human Rights said on Sunday 55 people had been killed, including 13 children and a pregnant woman, in a series of Russian airstrikes that hit residential areas in the previous 24 hours.
The anti-Islamic State activist group Raqqa is Being Slaughtered Silently also said the airstrikes were by Russian warplanes and put the number of deaths at 60.
The IS-affiliated news agency Aamaq said 43 were killed and 60 wounded.
A cessation of hostilities in Syria took effect three weeks ago, reducing violence but not halting the fighting as peace talks take place in Geneva. The deal does not include al-Qaida or Islamic State militants, whose de facto capital in Syria is Raqqa.
Russia has been pulling out its attack aircraft after announcing a partial withdrawal from Syria, where its air campaign in support of President Bashar al-Assad has turned fighting in his favour.
The Britain-based Syrian Observatory for Human Rights said that at least 39 people had been killed and dozens more wounded in the raids on Raqqa.
Separately, Russian warplanes hit the Islamic State-held historic city of Palmyra and its immediate vicinity with some 70 air strikes, the Observatory said, killing at least 18 Islamic State fighters.
Government forces and their allies are aiming to capture Palmyra, some 200km southwest of Raqqa and also held by Islamic State since May.
The Observatory said 16 people were also killed in air strikes in Raqqa on Friday.