France stepped up its bombardment of Islamic State targets in Syria after Friday's Paris attacks
Air
strikes by France and other nations on the Islamic State (IS)
stronghold of Raqqa in Syria since Sunday have killed at least 33
militants, activists say.
The UK-based Syrian Observatory for Human Rights said most died when checkpoints around the city were hit.It also reported the families of IS leaders had started leaving Raqqa for another of the jihadist group's strongholds, the Iraqi city of Mosul.
An IS-linked news agency has reported no casualties from the air strikes.
The Amaq agency said on Monday and Tuesday that French warplanes had only targeted "empty locations".
Installations 'stripped of personnel'
The Syrian Observatory, which has a network of informants on the ground, reported that more than 33 militants were believed to have been killed in the air strikes, but that their bodies were so severely dismembered that it was not possible to give an exact figure.
Some of the air and missile strikes may have been carried out by the Russians as well as the French, who began their bombing campaign on Sunday night, two days after IS claimed responsibility for the killing of 129 people in Paris, reports the BBC's Jim Muir in northern Iraq.
The Syrian Observatory also said that IS members and dozens of the families of senior members had begun leaving Raqqa for Mosul because of security concerns.
Our correspondent says the journey has been made more difficult by the capture by Kurdish forces last week of the town of Sinjar in north-western Iraq, cutting the last main direct route.
