Four youths are being hunted by police after a businessman was battered unconscious with a fire extinguisher on a commuter train.

CCTV images of the four, thought to be aged about 20, have been released today.

The victim was the sole occupant of a compartment in first class, reading a book as he returned home to Bognor from London on the 22:17 Victoria to Chichester service, when a gang of thugs went on the rampage.

They showered him with foam from a fire extinguisher which had been wrenched from its fixture.

The father-of-three, in his 30s, struggled to wrestle the canister away and was repeatedly hit over the head with it.

He blacked out and was found lying unconscious by train staff, who carried out first aid.

The train, which had just passed Worthing, pulled in at Ford station, where the victim was put into a waiting ambulance and rushed to St Richard's Hospital in Chichester.

He needed stitches to repair gashes to the back of his head and was kept in overnight for observation.

Police have now tracked down these images, taken from a CCTV camera at Littlehampton station earlier in the evening, of four youths matching the victim's description of his attackers.

They believe the four were returning to Littlehampton after spending about two hours in Worthing.

Detective Constable Darren Stenning, of British Transport Police, said: "It seems this was a vicious and unprovoked attack.

"The poor guy was travelling back from a hard day's work, reading his book, when he was set upon by four youths.

"It seems he was knocked unconscious for some time and doesn't remember anything about the incident after he was sprayed. He was hit very hard.

"These lads were on the train spraying everyone and we understand they assaulted another male before this, although he has not come forward.

"People just don't expect this sort of thing to happen when they get on a train."

He said the victim wanted the attackers to be caught, adding: "He was pretty shocked afterwards and I think his reaction was one of complete disbelief that it could have happened.

"He is a family man and he doesn't want this to happen to anyone else.

"This kind of thing does happen but it doesn't happen every night and we have police patrols on the trains."

All the attackers were white and aged about 20.

One was about 5ft 10in and broad with short, light hair. Another was described as slim, 6ft 2in with dark hair.

British Transport Police urged witnesses to call 0207 3915275 or Crimestoppers on 0800 555111.