LONDON (AFP) - British police said on Monday they had launched an investigation into reports of racist behaviour by Chelsea fans, weeks after their supporters were filmed blocking a black man from boarding a Paris Metro train.

British Transport Police were called to deal with claims that fans were behaving in a racist and abusive manner on a train from London to Manchester, northwest England.

Officers boarded the train in Stoke, central England, and asked four men to leave, according to a police spokesman. Four more fans left voluntarily.

"Shortly after 10.30pm on Sunday, March 1, officers were called to meet a Euston to Manchester Piccadilly train at Stoke, following reports of racist and abusive behaviour by a number of passengers, said to be football fans," explained the spokesman.

"Officers asked four men to leave the train at Stoke. We have spoken to two witnesses, and investigations continue." Premier League giants Chelsea had been playing in the League Cup final at London's Wembley Stadium, in which they beat local rivals Tottenham 2-0.

Footage posted online last month showed supporters blocking a man named as Souleymane S from boarding a train in the French capital and chanting: "We're racist and that's the way we like it".

The incident ahead of their Champions League draw with Paris St Germain sparked widespread condemnation.

Chelsea have promised to ban anyone proved to have been involved for life, while manager Jose Mourinho said the club were "appalled" by the behaviour.

British police are also seeking a group of men believed to be Chelsea supporters who were heard shouting racist chants at a London train station on their return from Paris.