A taxi driver protesting against Uber in Toronto was captured clinging on to a moving car for about 20 metres in a shocking video.

Taxi drivers in the Canadian city were gathering at the City Hall to protest taxi app Uber, which they say is stealing their business and flouting city bylaws.

The video by CBC News showed a taxi driver standing in front of a white car which had stopped at a traffic light.

"This is UberX," the taxi driver said to news cameras.

He began pounding angrily on the window of the car while trying to open the car door. When the light changed, the car drove off while the taxi driver was still latched onto its side.

It stopped at the next traffic light. When the car moved off from the junction, the taxi driver was left standing in the middle of the intersection, apparently unhurt.

He appeared breathless as he spoke to a reporter after the incident.

"We are trying to get a point across, that's what we're trying to do," he said.

Another video of the incident, taken by the passenger in the Uber car - Albert Kleyen - was posted on Facebook.

Uber has been operating in Toronto for about a year, The Huffington Post reported. In September, it was asked to cease operations while the city developed new laws for the service, but Uber continued to operate.

Taxi drivers stopped and slowed traffic in various parts of Toronto before heading to the city hall on Wednesday.

At least one other heated confrontation was captured on video.

Toronto Mayor John Tory has asked taxi drivers to "stand down", CBC News said.