A sleeping man was horrifically burned when a hooded gang attacked him on a train.

The 21-year-old was left fighting for his life after the cowardly attack on a train between Lancing and Worthing.

A train guard found him unconscious on the floor of a carriage after the attack on Sunday night. His face was seriously burned.

Detectives are hunting four youths who got on at Lancing at 7pm.

They are trawling CCTV footage and carrying out forensic tests on the carriage.

The victim was taken to Queen Victoria Hospital in East Grinstead, which specialises in treating burns. His condition was described as stable last night.

Detective Constable Rob Cager, who is leading the British Transport Police investigation, said: "It is believed there were at least four youths who boarded the train.

“The four youths approached the man who was subsequently assaulted while asleep.

“During the assault a fire was started just before the train pulled into Durrington-on-Sea railway station where the group fled the train."

Police have issued descriptions of three of the youths and are trying to identify them from CCTV footage of them boarding the train.

Two were white, about 14 or 15, with short black hair and black trousers.

Both wore hoodies, one black, one grey. One was about 5ft tall.

The third was about 17 or 18, about 6ft and skinny, also with short black hair.

He was wearing black jeans, a black hoodie and a black coat.

No description of the fourth youth has yet been issued.

DC Cager said: "This is a very serious offence. We are urging anyone who has information or who knows what happened to call us immediately.

“We would also appeal to the four youths to come forward."

Anyone with information should contact British Transport Police free on 0800 405040 or the Witness Appeal Line on 0207 3915275, quoting background log B2 of 08/12/2008.