Police are appealing for information about a suspect they want to trace after an officer was held down by two men and had his throat cut by a third.
Cleveland Police are looking for Aaron Gray, 30, who is thought to be in Middlesbrough, following the attack.
The officer was trying to make an arrest after seeing what he thought was a drug deal in Athol Street, Middlesbrough at around 8.30 on Saturday.
However, one man proceeded to punch him to the ground before two others pinned him down.
The man who hit him then held a knife to his throat and cut it while making threats.
Cleveland Police said the identities of two of those involved are currently unknown but they “urgently” need to locate Gray.
The officer was not seriously injured but left "very shaken", the force added.
Watch: Officer has face slashed as Manchester United anti-Glazer protests force Liverpool game to be postponed
Detective Superintendent Helen Barker said: “This was an incident which involved an officer who was simply carrying out his policing duties.
“Thankfully he was not seriously physically injured; however, understandably, he remains very shaken.
“He is recovering at home and has received many messages of support from colleagues across the force.
“We need to locate and speak to Gray as quickly as possible. We believe he remains in the local area, probably within Middlesbrough.
“People will know where he is, and I’d urge them to pass information to Cleveland Police via the 101 number.