There were more than 30 explosions heard in the Raqqa city area, said Rami Abdulrahman, head of the Britain-based Syrian Observatory for Human Rights.
It was not immediately clear if all the blasts were caused by air strikes or other weaponry. Islamic State is restricting movement inside the city, making it difficult to collect information on any casualties, Abdulrahman added.
Writing on Twitter, the anti-ISIL activist group Raqqa is Being Silently Slaughtered said air strikes had also hit a stadium, a museum, clinics, a hospital, a chicken farm and a local governmental building.
Water and electricity were cut across the city as a result of the raids, the group said, adding that at least 30 air strikes had been carried out.
The group said no civilian casualties had been immediately reported.
Speaking on the sidelines of the G20 summit in Turkey, French foreign minister Laurent Fabius said France had the "legitimacy" to take action against Islamic State after Friday's terror attacks in Paris.
He said the decision to conduct the airstrikes was a "political" one and that France had to be "present and active" following Friday's attacks which killed more than 130 people.
Al Jazeera and wire services