British Transport Police have released CCTV images of four men they want to speak to in connection with a string of alleged assaults on train staff in Kent.

Detectives say that in one incident in August, a man threatened to headbutt and stab the driver of a Southeastern train from Strood to Paddock Wood.

Earlier in the month, another employee is said to have been punched in the face at Whitstable train station, while a conductor was allegedly slapped around the head while checking tickets at Rainham in April.

Det Sgt Leigh Marshall of British Transport Police said: "We're asking for help from members of the public to help us identify these men. If you know any of them and can tell us who they are, we want to hear from you."

He added: "It's not clear why people feel they have the right to attack people who are simply trying to do their jobs, but we'll do all we can to track them down."

Anyone with information about any of the incidents or who recognises anyone in the CCTV images should contact British Transport Police on 0800 405040, quoting reference number B12/LSA.