A woman has been sexually assaulted in the centre of Northampton.
The incident happened in St Giles Street between 2300 BST on Saturday and 0135 BST on Sunday.
The woman was walking along the street when a man approached her from behind, lifted her skirt and "touched her inappropriately" said police.
The man is described as black, 5ft 6in (1.7m) tall, with a stocky build. He was wearing dark tracksuit bottoms and a dark shiny hooded top.
He ran off alone towards St Giles Terrace.
Moments after the assault, a gold-coloured three-door Vauxhall car appeared from the direction in which the man had run.
The occupants of the car, who were all male, all made comments about the woman, said police.
Anyone with information is asked to call Northamptonshire Police.