These three men could provide vital clues to an investigation to find the killer of a police station cleaner.

Enayit Khalili, 26, - who worked at Cowley Police Station - died from a single stab wound when he answered the door to his home in Fiennes Road, Rose Hill, in Oxford, in March.

Today DI Colin Seaton, of Major Crime Unit, appealed to these three unknown men to come forward because they may have vital information to help catch the killer.

DI Seaton added the men are not suspects but were seen chatting to Mr Khalili in an Oxford bookmakers in the days leading up to murder.

Detectives working on the case have issued a £5,000 reward for any information which leads to an arrest or conviction.

DI Seaton added: "It is important we find these three men because we believe they may be able to add something to the investigation.

"They certainly appear to have known Mr Khalili and any information that they have I believe will be useful for us."

Police believe Mr Khalili knew his killer and need to interview these three men in a bid to help build up the background information on Mr Khalili including known associates and where he spent time.

Mr Khalili was originally from Afghanistan before gaining asylum in the UK and hundreds of appeal posters in his native language Dari have been placed around the city.

Witnesses can also leave messages or information in Dari on hotline number 07796091235 and email enayitmurder@thamesvalley.pnn.police.uk Anyone with information on the murder can also contact police on 08458 505505 or anonymously to Crimestoppers on 0800 555 111.