Toronto police are asking for the public's help identifying a suspect in what they describe as an unprovoked attack on a demonstrator in downtown Toronto on Saturday.

Investigators say the victim was walking northbound on Yonge Street near Grosvenor Street, speaking with another demonstrator, when a man approached from behind and punched him several times in the head. The victim fell to the ground, sustaining injuries to his face and leg.

Police describe the suspect as about five feet five inches tall with a thin build and black hair. He was last seen wearing prescription glasses, a grey jacket and dark grey sweatpants, and carrying a black Under Armour backpack.

Anyone who recognizes the suspect or witnessed the attack is asked to contact Toronto police. No further details about the victim's condition were released.