Montreal police are seeking the attacker in an armed assault in the Plateau that has left one person in critical condition.

Police say a man in his late thirties was stabbed at about 8:30 p.m. Thursday at the corner of Prince-Arthur St. and de Bullion.

The assailant fled the scene before police arrived.

Paramedics rushed the victim to the hospital, where he was treated for severe injuries to his upper body.

Police blocked off the square for several hours while they searched for clues and gathered evidence.