A wave of US-led air strikes have struck at least 30 targets around the Syrian city of Raqa, the self-proclaimed capital of the Islamic State group, a monitor said Sunday.

The Syrian Observatory for Human Rights said the strikes took place before midnight Saturday and hit 30 targets on the northern outskirts of Raqa.

They also hit Division 17, a Syrian army base the jihadist group captured earlier this year.

Observatory director Rami Abdel Rahman said the strikes had caused casualties but there was no immediate toll.

"The strikes hit IS positions, and there are certainly casualties among their forces," he said.

The waves of hits was one of the larger actions carried out by the coalition, Abdel Rahman added.

"We can't say it's the largest set of raids they have carried out, but it's been a long time since we've seen this number of targets hit," he said.

The US-led coalition began carrying out air strikes against the Islamic State group on September 23.

The strikes have killed at least 963 people, including 838 IS jihadists and 72 members of Al-Qaeda's Syrian affiliate Al-Nusra Front.

Another 52 civilians have also been killed, along with one Islamist rebel, according to the Observatory.

Syria's regime has also continued to hit IS in Raqa, though its raids have regularly killed large numbers of civilians.

The Observatory said regime planes carried out one strike in Raqa on Saturday that killed at least seven civilians.

And on Wednesday, regime raids on Raqa killed at least 95 people, over half of them civilians, the monitoring group said.