A woman was left with a fractured skull after an assault in Old Bedford Road on Sunday.
The victim, 25, and her friend, who are both Portuguese and speak very little English, were walking near Coupees Path at around 5am when four men pulled up alongside them in a car.
An altercation took place between the two groups before one man struck the woman across the head with a bottle, knocking her unconscious.
The men then got back into their car and fled the scene.
Det Con Colin Knight said “This was a shocking assault on a young lady who had been enjoying a night out in Luton with friends. She has been left with some very serious injuries and it is imperative that we find the person responsible for this attack as quickly as possible.
“We believe that an argument had taken place between the victim and the offender in the Exchange in King Street earlier on in the evening and it appears that the offender sought a very violent retribution.”
The victim was taken to hospital for treatment to fractures to her temple and a suspected bleed on the brain. She remains in hospital in a stable condition.
Det Con Knight said: “I urge anyone who witnessed this assault or has any information about the offender and his friends to come forward as soon as possible – even the smallest piece of information could be useful.”
The offender is described as an Asian male, in his mid to late 20s, five feet five inches tall, muscular build, with tattoos on his arm, wearing a white short sleeved shirt, jeans and with a gold bracelet on his wrist.
Call 01582 394069 in confidence or text information to 07786 200011.