Suspected Russian air strikes killed at least 10 civilians Saturday in a village held by the Islamic State group in the eastern Syrian province of Deir Ezzor, a monitor said.

The Syrian Observatory for Human Rights said three children were among those killed in the raids on Al-Hisan in the western part of the province.

Much of oil-rich Deir Ezzor is controlled by the jihadist group which has also begun an offensive to wrest the provincial capital of the same name and the nearby military airport from government hands.

Russia launched air strikes in Syria in September in support of President Bashar al-Assad's regime.

It has stepped up its air raids on areas held by IS and rebel groups battling the regime in recent months.

According to the Observatory, suspected Russian air raids killed 54 civilians in various parts of Syria earlier this week, including in Deir Ezzor.

On Saturday the head of the Britain-based monitoring group, Rami Abdel Rahman, said four months of Russian strikes in Syria have killed 3,578 people -- 500 more than a previous toll on January 20.

Of the total he said 1,380 are civilians -- 332 children, 195 women and 853 men.

The raids also killed 965 IS fighters and 1,233 other opposition militants, including members of Al-Qaeda affiliate Al-Nusra Front.

On January 20, the Observatory, which relies on sources on the ground for its information, said Russian air strikes since September had killed 3,049 people.

The latest developments come as representatives of Syria's main Saudi-backed opposition body arrived on Saturday in Switzerland for UN-organised peace talks.

More than 260,000 people have been killed in Syria's conflict, which erupted nearly five years ago with anti-government protests.

Millions have been displaced or forced to flee the devastation.