A man had his mobile phone and cash stolen in a robbery in Finland Way, Corby, in the early hours of Saturday, February 28.
At about 3.15am, the victim was walking down an alley towards Finland Way when a man rode past on a bike.
The man waited for him and, as the victim walked past, the man punched him, grabbed him around the neck and threatened him with a sharp implement while demanding money.
The offender stole cash and the victim’s mobile phone before making off.
He is described white, 6ft to 6ft 2in, with a slim build. He was wearing black clothing, had dark stubble and spoke with a Corby accent.
Officers have also released a CCTV image of a person on a bike who was in the area around the time at the robbery.
Witnesses, or anyone with information, are asked to call Northamptonshire Police on 101.
Alternatively, phone Crimestoppers on 0800 555 111 or use the online form at www.crimestoppers-uk.org.