Police were this evening urging calm in a North-East town after the father of a 12-year-old girl was stabbed to death in a busy street.

John Paul Robertson, 37, of Brinkburn Road, Darlington, believed to be a bouncer in a town centre pub, was found bleeding to death just yards from Cockerton Police Station at 7am on Saturday morning.

Police today confirmed that part of their inquiry was concentrating on the simmering tensions between a group of travellers and a gang of towns people.

A 33-year-old man, accompanied by his solicitor, came into Darlington Police Station at 2pm on Saturday.

He spoke to officers working on the case and was arrested on suspicion of murder. He was still being questioned last night.

Mr Robertson, who has a 12-year-old daughter, is believed to have been dragged into an alley on the junction of West Auckland Road and Willow Road, just yards from Cockerton Police Station, before being stabbed in the neck and left for dead.

Detectives said there were indications that the bricklayer had staggered a few yards into the middle of the road and collapsed, before a passer-by stopped to help.

The witness alerted a female police officer, making her way back to Cockerton police station, and she made attempts to resuscitate Mr Robertson before an ambulance arrived. Chief Superintendent Michael Banks, of Darlington Police, said that clashes between rival gangs was "one of the lines of inquiry" in the investigation.

Police are investigating whether it is linked to events in August, when armed police staged a four-hour stand-off outside a property in Haughton after reports of gunshots being fired. The rival gangs were rumoured to be planning a massive brawl on the August Bank Holiday Monday, but extra riot police were drafted in and the fight never materialised.

Trouble between the rival gangs, one known as "townies" and the other, from the travelling community, dubbed "hawkers", was blamed for the murder of David Edmondson, who was beaten to death in Darlington town centre in 1994.

The killing sparked off rioting, involving hundreds of people, in the town centre, which was only quashed by hundreds of riot police being drafted in from all over the North-East.

Chief Supt Banks said: "There has been, traditionally, over the years, some tension between a certain group of people within the town and the travelling community.

"That tension was heightened in the incidents that occurred over the August Bank Holiday period.

"But I am reassured in my own mind that order and safety will be maintained."

Police are appealing for anyone else with information to come forward and help with inquiries. The incident room can be reached on (01325) 467681.