A fourth man was today arrested in connection with the murder of an Iranian asylum-seeker, police today said.

Tayman Bahmani died in hospital from a single stab wound in what police are treating as a ''racially motivated'' attack.

An 18-year-old man was arrested in Edinburgh in the early hours of this morning and was being brought back to the Northumbria Police force area for questioning.

Three other people, two men and a woman, were continuing to be questioned in connection with the fatal stabbing after officers were granted an extended licence to hold them in custody which will last until Saturday lunchtime.

Mr Bahmani, 30, who fled to Britain from his native Iran two years ago, died after a confrontation between two groups one white, the other Iranian men in Peel Street, Hendon, Sunderland, on Wednesday afternoon.

He was rushed to Sunderland Royal Infirmary after being stabbed but later died.

Police have yet to officially name the dead man, but an ethnic rights organisation, The Monitoring Group, released his name yesterday. A Northumbria Police spokeswoman said additional forensic experts were today being drafted in from London to help with the inquiry.