A man is being treated for head and face injuries after an apparent one-punch attack in the Brisbane CBD.

Emergency services rushed to Ann Street, near Anzac Square, following the attack on Mark English about 4pm on Monday.

Paramedics treat Mark English, allegedly coward punched on Ann Street in the Brisbane CBD. Credit:Jorge Branco

He lay motionless, face-down on the ground for at least five minutes as paramedics assessed his injuries.

The man's partner, Varri Telfer, said a close relative of the victim had run across the street from the Grand Central Hotel and attacked the man after seeing him for the first time in four years.