MURDER squad detectives have called on the criminal underworld to help them find the killer of a Southamp-ton teenager.

They have appealed to anyone with information on who stabbed 18-year-old Mikhail Thomas to death to come forward.

Police last night formally named the youngster, who is from the Southampton area, after a post-mortem revealed he had died of a single stab wound.

Det Insp Paul Barton wants to hear from anyone who saw three men involved in a dispute in the Cranbury Avenue and Derby Road area of Newtown on Wednesday at 11pm.

Drug dealers and prostitutes are known to use those roads.

"We are aware there may be a number of people who frequent that area who may have their reasons for not wanting to come forward," he said

"We want to hear from them, as well as any local residents who may have seen something."

Police believe Mikhail was involved in the dispute before being stabbed in the Denzil Avenue, Cranbury Avenue or Derby Road area.

He was driven by an acquaintance in a blue Rover car to the Royal South Hants Hospital at 11.27pm and treated by paramedics before being rushed to Southampton General Hospital, where he was pronounced dead shortly after arrival.

The driver of the vehicle is helping police with their inquiries but is not under arrest.

Police have not found a murder weapon and have no idea of the killer's motive.

Det Insp Barton said: "We don't know what the motive is. We are keeping an open mind. If the people who did this are local, residents are going to start hearing things.

"We want anyone who saw or who hears anything about what happened to come forward."

Teams of specialist officers with dogs sealed off a 200-metre stretch of Derby Road as they carried out a fingertip search of the area up until yesterday evening.

In total 30 officers are working on the case including detectives from the Major Crime Department, local uniform officers and staff from the Netley-based Force Support Unit.

They will be carrying out house-to-house inquiries over the next few days and distributing witness appeal letters to local residents and businesses.

Police are also working closely with community leaders in a bid to reach members of the area's Asian, Jamaican and East European communities.

If you can help call Operation Holbrook at Southampton's Major Incident Room at Hulse Road on 0845 045 4545 or Crimestoppers anonymously on 0800 555 111.