Thames Valley Police is appealing for witnesses to an assault in Milton Keynes on Sunday (10/4).
Sometime between 9.30pm and 10pm, the victim, a man aged in his late teens, was approached by an unknown man from behind outside Co-op Food on St Ledger Drive, Great Linford.
When the victim turned round, he was slashed in the stomach with a knife.
The victim was taken to Milton Keynes University Hospital for further treatment but has since been discharged.
The offender is described as around 5ft 10ins tall, of slim build, wearing an all-black tracksuit and a black ski mask with just his eyes showing.
Detective Inspector Jason Simpson, based at Milton Keynes police station, said: “I would like to reassure the community that we are investigating this assault thoroughly and robustly as we will not tolerate knife crime in Milton Keynes.
“I am appealing for any witnesses or anyone with information about it to please get in touch.
“If you have any CCTV footage in the area or any dash-cam footage if you were in the area around the time, I’d also ask that you check any recordings in case it has captured something that could assist our investigation.
“To contact us, call 101 or make a report on our website, quoting reference number 43220155017.
“Alternatively, you can provide information anonymously to the independent charity, Crimestoppers, by calling 0800 555 111 or via its website.”