FOUR men have been cleared of involvement in the killing of an Oxford police station cleaner after they told detectives he was attacked when he answered the door at his home.

Enayit Khalili, 26, a refugee from Afghanistan, died from a single stab wound to the stomach at a house in Fiennes Road, Rose Hill, in March.

Police have no suspects under arrest on suspicion of the murder, but say they are continuing to follow a number of leads.

One of the freed men, Khodadad Rezaie, 28, said he was a housemate of Mr Khalili and believes a stranger stabbed him to death.

He said: "I was upstairs sleeping and he went down to open the door. Then he came back up, saying 'please call me an ambulance'. That's what happened that night."

Police would not comment on any lines of inquiry.

The four men held by police were either friends of Mr Khalili, or inside the house at the time of the attack.

Yesterday, a 36-year-old man, who described himself as a friend of Mr Khalili, but was not a suspect, said: "We feel really bad about the murder. Those guys in the house were his friends and they are very sad as well. We are all keen they find the real killer.

"I understand they told police during interviews somebody knocked on the door and when Enayit opened it he was stabbed.

"Then he came upstairs and said 'don't go outside' and collapsed."

Thames Valley Police spokesman Toby Shergold said officers released four men aged 19, 21, 28, and 35 - all believed to be Afghans - without charge on June 11. They had been on police bail since March.

Two other men, aged 22 and 24, also arrested on suspicion of murder, were released in March.

Det Insp Colin Seaton, of the major crime squad, said: "Our investigation continues and this case is very much still active, so we cannot discuss specific details at the stage.

"However, we can say we're working closely with Enayit's associates, his family and members of the Afghan community in Oxford and elsewhere and are progressing several lines of inquiry."

Mr Khalili, 26, was stabbed in the early hours of Saturday, March 24. He died 20 hours later.

In the weeks after the killing, police said they had not found a weapon or motive for the killing and Mr Khalili's brother Sedigh Mansoorian and cousin Hassan Mohammadi made appeals for information.

Mr Khalili was a cleaner at Cowley police station and was sending money back to his family in Pakistan. He also worked as a waiter at Oxford Greyhound Stadium.

He was a keen volleyball player and also practised marital arts.

Mr Khalili sought asylum in the UK in 2001 and was subsequently given permanent leave to remain here.

Anyone with information about the murder should call Det Insp Seaton on 08458 505505 or the confidential Crimestoppers line on 0800 555111.