Police said officers were called to Bohemia Road at the junction with White Rock Road, outside the ambulance station, where the 42-year-old local man had sustained stab wounds to his chest and leg.
He is receiving treatment at hospital for the injuries which are not assessed as life-threatening.
Police said his attackers were described as two white boys, aged about 16-17, both about 5ft 7ins tall.
One was possibly wearing a red coat and they are believed to have been with a third boy.
Detective Constable Andy Smithson said: “If you were in the area at that time, or if you have any other information, please contact us either online or by calling 101, quoting serial 214 of 07/11.