UP to 20 Middlesbrough football fans may have seen a confrontation in which a North-East man was murdered and his friend seriously injured.

Police say it is crucial they trace the supporters who were in Amsterdam's Bar Pinockio, where Brendan Michael O'Connor, from Middlesbrough, was having a drink with friends moments before he was stabbed to death in a nearby alleyway.

The 36-year-old BP quality control worker died from a single stab wound while his friend, BT business manager Howard Boville, 38, was stabbed twice. His injuries are not thought to be life-threatening.

The men had flown to Holland with their wives to watch the Boro Uefa cup tie against AZ Alkmaar on Thursday. Unable to buy tickets for the game, the four friends decided to visit the centre of Amsterdam.

They visited Bar Pinockio, a typical small bar in the city centre, only 20 yards from the alley where "Bren" O'Connor was later killed.

Both Mr O'Connor and Mr Boville had followed a Dutch national out of the bar when there was an argument in the street outside.

The man held by Dutch police for the attack is a tall, muscular, shaven-headed black man who wore a distinctive blue anorak with a VW car logo on the back.

Detective Chief Superintendent Mark Braithwaite, head of crime and operations with Cleveland Police, said he could not speculate on the reasons for the altercation or the stabbings that followed, but it is thought the 42-year-old suspect, being held by Dutch police, may have been trying to sell drugs to the men.

Mr Braithwaite said: "It is my understanding that there were around 20 Middlesbrough supporters in the bar, and it is crucial that we trace all those that were inside this bar."

While Mr O'Connor came from Middlesbrough, and Mr Boville lives in Eaglescliffe.

Mr Braithwaite said: "My appeal today is to trace who might have been in Pinockio's bar on Thursday night, and the reality is people there could have come from all over the country.''

Mr O'Connor's parents, who live in Acklam, Middlesbrough, flew out to Amsterdam at the weekend to formally identify their son's body and to lay flowers in the alley.

While two senior police officers flew to Amsterdam to help their Dutch colleagues, Cleveland Police have provided an officer to help Mr O'Connor's wife, Tania, and family.

Although from Teesside, Mr O'Connor had been living with his wife in the Camden Town area of London. They have no children.

Both Mr Boville's wife, Helen, and daughter are at his bedside in Holland.

Mr Braithwaite said of Mr O'Connor's murder: "His death is an isolated criminal act and nothing to do with football at all. This confrontation could have happened to anybody at any place in any town centre.

"My Boville managed to stagger back to the top of the alley. An ambulance containing a doctor was quickly on the scene and immediate first aid was given but, sadly, Mr O'Connor died of his injuries."

Police yesterday released photographs of Bar Pinockio and Hunter's Bar, which is opposite the alley, to jog the memories of fans.

Anyone who can help the police is asked to call (01642) 301333.