A 20-year-old man was stabbed in his back during a robbery.

Police say the man sustained a "small wound" during the incident which happened on the Watford and Croxley Green border.

At around 2.55am on Saturday (June 27) two men and a woman were walking over a canal bridge off the A412 Watford Road.

The group of friends were approached by a group of six to seven males who asked them for cigarettes.

One of these men allegedly produced a knife and demanded items from the victims.

They stole a mobile phone and a black bag from a 20-year-old man, while a black Fred Perry jacket was forced off another man, also 20.

Police say as the jacket was taken from him, the man sustained a wound to his back.

The robbers left the scene and the police were called.

Four males have been arrested in connection with the robbery.

They are aged 21, 19, 17, and 16, and they have all since been released on bail.

Enquiries continue and detectives are appealing for any witnesses.

Detective Constable Steve Mason, from the Three Rivers local crime unit, said: "Our enquiries are continuing at this time and we are appealing for anyone with information to please come forward. I appreciate the incident occurred during the early hours but anyone who was in the area may have seen this group around. Any information could greatly assist us."

Anyone with information is asked to email steve.mason@herts.police.uk, call 101, quoting 41/50139/20 or call Crimestoppers anonymously on 0800 555 111.