Ontario's police watchdog is investigating after a man suffered a serious facial injury during a police raid.

The Special Investigations Unit says the injury occurred early Thursday morning when officers from London, Ont., were helping Toronto police execute a search warrant at an apartment in Toronto as part of an investigation into a street gang with links across the province and Western Canada.

Hundreds of police officers descended on nearly 80 homes across Ontario on Thursday as part of the Project Kronic investigation targeting the Driftwood Crips.

The SIU says officers interacted with the man, whom police believe to be in his 60s, and he was injured and taken to hospital. 

The SIU investigates reports of death, serious injury and sexual  assault involving police.