US denies conducting deadly Syria strikes

"Russian-backed pro-regime forces are conducting operations in Deir az-Zour and the coalition does not support pro-regime operations," said coalition spokesman Ryan Dillon.

The strikes on Deir az-Zour, 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 – a claim denied by the coalition.

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

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 az-Zour 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 az-Zour province.

A second, separate offensive against the militants 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 az-Zour province, its last remaining stronghold in the country after the SDF ousted it from its bastion Raqqa last week.

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

Agencies contributed to this report