The US-led coalition battling the Islamic State group in Syria and Iraq denied on Tuesday that it had carried out deadly air strikes around the Syrian city of Deir Ezzor.

The strikes on Deir Ezzor, where Syrian regime forces backed by Russia have seized most of the city from IS, were reported late on Monday by a monitoring group, a local official and Syrian state television.

The Syrian Observatory for Human Rights said 22 civilians were killed in strikes by unidentified aircraft in the Al-Qusur neighbourhood, in the west of the city.

A local official said 14 people were killed and blamed coalition strikes.

"The allegation that a coalition strike may have killed 14 civilians and wounded 32 others in Deir Ezzor is false," coalition spokesman Ryan Dillon told AFP.

"Russian-backed pro-regime forces are conducting operations in Deir Ezzor and the coalition does not support pro-regime operations," he said. 

Dillon said the coalition had carried out only one strike in the area in the last two months, on September 16 in support of US-backed forces fighting IS east of the city.

Syrian regime forces backed by ally Russia have seized most of Deir Ezzor city after breaking an IS siege of nearly three years on government-held districts in September.

The regime offensive against IS, backed by Russian airpower, is being waged largely on the western side of the Euphrates river that cuts diagonally across Deir Ezzor province.

A second, separate offensive against the jihadists is being fought on the eastern side by the Kurdish-Arab Syrian Democratic Forces, backed by the coalition.

A "deconfliction" mechanism is meant to keep the two campaigns separate.

IS controls less than half of Deir Ezzor province, its last remaining stronghold in the country after the SDF ousted it from its bastion Raqa last week.

More than 330,000 people have been killed in Syria since the war began in March 2011 with anti-government protests.