Damascus, Nov 18 (IANS): Scores of families of Islamic State (IS) militants and commanders have started relocating from Syria to Iraq after heavy French air strikes, a monitor group reported on Wednesday.

Most of those families are either foreign or Arabs and have chosen to relocate from Syria's northeastern province of al-Raqqa, the de facto capital of the IS, to the Iraqi city of Mosul, Xinhua quoted the Syrian Observatory for Human Rights as saying.

The Britain-based watchdog group said these families claim that Mosul, which is also under IS control, was safer than al-Raqqa, which has been heavily pounded by French air strikes following the November 13 terror attacks in Paris that claimed at least 129 lives and for which the terror group claimed responsibility.

The observatory, which relies on a network of activists on ground, said at least 33 IS militants were killed over the past three days as a result of the intensified French air strikes.

On Sunday, French warplanes commenced retaliatory strikes against the IS, hitting the terror group with 30 air strikes in a single day.

The strikes targeted the city of al-Raqqa and its surroundings, amid a state of alert among IS militants in the city, according to the observatory.

The French Defence Ministry said on Sunday that warplanes conducted a series of "massive" airstrikes on al-Raqqa, destroying a key IS command centre and a training camp.

"The raid, conducted by 10 fighter jets, was launched simultaneously from the United Arab Emirates and Jordan. Twenty bombs were dropped," a statement said.