A woman has been dragged into an Essex nature reserve and sexually assaulted by two men in an ordeal lasting several hours.
The victim, who is in her 20s, was walking along a footpath in Central Park, Chelmsford, on Friday night when the attack happened.
The men ran away when they heard a group of young women walking along the path from the town centre.
Police are appealing for the group of girls to come forward.
The attackers are described as white, in their mid to late 20s, of medium build with dark hair and about 5ft 7in (1.7m) tall.
Both were wearing jeans, one with a black t-shirt, the other with a white checked shirt.