A man was hospitalised after being attacked in St Neots on Saturday.
The 31-year-old was walking near the Bridge House, in Market Square, when the attack happened between 10pm and 11.30pm.
A spokesman for Cambridgeshire Constabulary said: “It is not known how many attackers there were and there are no further descriptions.”
The spokesman said the man was treated for serious injuries in hospital before later being discharged.
Anyone who was in the area and thinks they may have information should contact PC Andy Minns on 101 or Crimestoppers, anonymously, on 0800 555111.