The extremist group has controlled the city in northern Syrian since 2013 and considers it the capital of its self-styled caliphate.
The Britain-based Syrian Observatory for Human Rights, which documents the conflict through activists on the ground, said 55 people have been killed, including 13 children and a pregnant woman, in a series of Russian airstrikes that hit residential areas.
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.
