The two 18-year-olds were waiting for a train about 2.30am when two men standing on the other platform began yelling at them before jumping onto the tracks and running to their side.

One of the men grabbed one of the teens and demanded he hand over his mobile phone before hitting several times in the face and head.

The attacker snatched a phone and a wallet from the injured man while the other stopped his mate from coming to help.

Police have described the attacker as about 20, with brown hair and a fair complexion. He was wearing a black and orange work shirt.

Contact Crime Stoppers on 1800 333 000.