A 35-year-old man was assaulted by men carrying poles or cricket bats in an open grassed area in Wolverton on Sunday.
It is thought that around 9.15pm a Land Rover Discovery was parked up in the grassed area in Horners Croft and the victim was pushed onto the bonnet of the vehicle by two or three men.
The victim then ran away. He suffered head and wrist injuries and was taken to the John Radcliffe Hospital in Oxford for treatment where he remains.
One of the offenders is white, stocky, aged 30 -35 and 5ft 10ins. Two of the offenders are black and one was wearing a cream Stone Island jacket.
They were carrying either poles or cricket bats.
Police would like to speak to anyone who witnessed the incident or who has any information about what happened.
Det Sgt Phil Walsh said: “The victim sustained serious injuries in this assault and it is vital that we trace the offenders.
“I would like to speak to anyone who was in the area around the time of the incident, who saw or heard anything out of the ordinary. Please contact police via the 101 number.”