A shop owner had part of his thumb severed when he chased would-be robbers from his store.
The man had to be rushed to hospital for emergency surgery following the attack late last night.
A gang of four or five men went into the convenience store in Wibsey Park Avenue, Wibsey, at 10.45pm last night and started shouting, before a fight broke out.
The victim sounded a panic alarm and followed the men after they fled. He followed them briefly before returning to lock the shop, which is when he noticed blood coming from his right hand and saw part of his thumb had been severed.
He was taken to hospital for emergency surgery and is currently in a stable condition.
The suspects are described as Asian, in their mid to late teens, skinny and around 6ft. They were wearing dark hooded tops with the hoods up and dark tracksuit bottoms. They were last seen running down Wibsey Park Avenue towards Farfield Avenue.
Two were believed to be wearing face coverings.
Detective Chief Inspector Tony Nicholson, of Bradford District CID, said: "We would like to hear from anyone who saw a group of men acting suspiciously in Wibsey Park Avenue in the time leading up to, or just after this incident occurred.
"The shop assistant sustained a nasty injury to his thumb and we are keen to trace these men to prevent any similar incidents from occurring.
"Patrols have also been increased in the area to offer reassurance to residents.
"Anyone with information is asked to contact Bradford District CID on 101 or Crimestoppers anonymously on 0800 555111."