The shooting began in front of a bar in Greektown in the city's Riverdale neighbourhood, and as many as 10 people may have been shot, the Toronto Sun reported.
Victims, possibly including children, were reported to be spread over several blocks and a number sustained significant injuries, paramedics reported.
The Star reported witnesses as saying a man dressed in black fired up to 20 shots in the area.
At least eight people have been shot in the Canadian city of Toronto, according to reports.
The shooting is believed to have happened just after 10pm local time, when police were called to reports of shots being fired near the Brass Taps Pizza Pub, which is in the city's Greektown area.
CP24 said at least eight people, including one child, had been taken to hospital with injuries.
According to paramedics quoted in local news reports, the crime scene covers several blocks.
Witnesses told the Toronto Star that a man dressed in black had fired a gun multiple times, some estimating that he fired up to 20 shots.
Unconfirmed reports say the shooter is no longer active.