Police have issued CCTV images of people they hope might be able to provide vital clues to a knifepoint sex attack in County Durham.

The assault on the 19-year-old woman took place early on 4 August in the West Lane area of Chester-le-Street.

Detectives have been studying hours of CCTV footage, in a bid to trace potential witnesses.

They are asking two men seen on board a night bus and a woman spotted on Front Street in the town to come forward.

The men, possibly in their twenties, were shown about to disembark from the Newcastle to Durham number 21 night bus in the town centre at 0349 BST.

The woman, wearing a light coloured coat or jacket, was walking past the Argos store on the Front Street at 0429 BST.

Det Insp Kevin Langan said: "The response to the posters and other publicity has been very encouraging with several names put forward, but we would like to speak to the people on these photos as a matter of urgency.

"I must stress we are treating the woman outside Argos and the two men on the bus solely as potential witnesses.

"It is possible they saw the man who carried out the assault and for that reason I would value their assistance."

Extra police patrols will be in place around the town's bars and clubs on Friday night to talk to any drinkers or revellers who can help the investigation.

The attacker is described as aged about 40, 6ft (1.82m) tall, and of stocky build with very short shaved hair.

He was wearing a long sleeved dress shirt.