Air strikes by the US-led coalition on an eastern Syrian town held by Islamic State are reported to have killed at least 35 people.

The UK-based Syrian Observatory for Human Rights said 26 people were killed when a four-storey building was destroyed in an air strike.

It said nine died in another strike on a nearby market in the town of Mayadeen on Thursday night.

Syria's state news agency SANA also said 35 civilians, most of them women and children, were killed in the air strikes.

Reports of deaths among civilians have been on the rise as the fighting against IS intensifies in northern and eastern Syria.