A 22-year-old woman has been sexually assaulted by a stranger, who attacked her from behind.

The incident happened in Blackbird Leys at about 1.15am on Saturday after the victim got off a bus in Field Avenue.

A member of the public shouted at the attacker and he walked off, police said. Police described the attacker as dark-skinned, about 5ft 8ins and in his late 20s.

Call 101 with any information.