As a six-day old blockade of North America's busiest trade corridor ended on Sunday, Canadians voiced questions on policing tactics used to quell the demonstrations in the border city of Windsor and in Ottawa where protests entered a third week.

The "Freedom Convoy" protests, started by Canadian truckers opposing a vaccinate-or-quarantine mandate for cross-border drivers, have turned into a rallying point for people opposing the policies of Prime Minister Justin Trudeau's government, covering everything from pandemic restrictions to a carbon tax.

Meanwhile a social media outcry has been triggered by images of police mingling with a sea of protesters in Ottawa, helping some put a fallen tent back up, and one video showing an Ontario Provincial Police officer telling demonstrators "I support you guys 100%."

The police department said the officer's comments were "not in line with the OPP's values" and they were investigating.

At least two members of Canada's Special Operations Forces are also under investigation for allegedly supporting the protests, the military said.

Hundreds of counter-protesters on Sunday blocked vehicles trying to join the protest in downtown Ottawa, frustrated by what they said was police inaction.

"We need to come together as people and say this will not stand," said one demonstrator in front of the city's police headquarters who said he was an Ottawa resident, but declined to give his name, fearing reprisals. "We need the police to actually support the oath that they took to support this community and if they can't do that, then they should resign."

Police in Windsor cleared the Ambassador Bridge, a vital trade route to Detroit, peacefully two days after the province of Ontario declared a state of emergency and the city got a court injunction to end the protest.

The bridge blockade choked the supply chain for Detroit's carmakers, forcing Ford Motor Co, the second-largest U.S. automaker, General Motors Co and Toyota Motor Corp to cut production. The estimated loss so far from the blockades to the auto industry alone could be as high as $850 million, based on IHS Markit's data.

The jurisdictional overlap between, federal, provincial and local policing has been blamed for the response by police in Ottawa.

A federal minister described a lack of law enforcement in the capital as "inexplicable."

"I will tell you the country needs the police to do their job," said Emergency Preparedness Minister Bill Blair, who previously led Toronto's police force, speaking to a local TV channel on Sunday.

"We need them to enforce our laws, to restore peace and order at our borders and in our cities, and we need them to use the tools that are available to them."

Windsor Police said that throughout the demonstration, police have respected the protesters' freedom of expression and their right to a peaceful assembly. Before the Ambassador Bridge was cleared, there was a tense standoff between police and the protesters for more than 24 hours. The police arrested 20 to 30 people, but there were no reports of violence.

"The importance of public safety remained the number one priority of officers with the goal being a peaceful resolution," a police statement said on Sunday.

Protesters have also shut down smaller border crossings in Alberta and Manitoba last week and, on the weekend, shut down the Pacific Highway border point in British Columbia.

($1 = 1.2721 Canadian dollars)

(Writing by Denny Thomas; Editing by Amran Abocar and Kenneth Maxwell)