Truckers opposed to vaccine mandates have blocked streets and set up camp in the city since 29 January - and the failure of Police Chief Peter Sloly to break the siege early on has angered residents.

Mr Sloly, who was accused of being too permissive in his approach, had argued his police force lacked the resources to peacefully disperse the protesters amid fears the use of force could stoke violence.

It comes as Prime Minister Justin Trudeau invoked emergency powers in a bid to end the occupation in the capital - and elsewhere across the country - and cut off protesters' funding.

Thousands have descended on Ottawa to join the truckers who have been encamped outside parliament for weeks.

The movement - a protest against vaccine requirements for lorry drivers travelling across the border into the US - has spilled into other Canadian cities, and triggered copycat convoys around the world including in France, New Zealand and the Netherlands.

The protests have also morphed into broader demonstrations against other coronavirus restrictions.

Public safety minister Marco Mendicino said the Emergencies Act would give police authority to begin towing away vehicles.

"We need law enforcement to take the reins, to utilise the Emergencies Act and to enforce," he said.

"We have given new powers to police and we need them to do the job now."

It follows the arrests of 11 people at the blockaded border crossing at Coutts, Alberta, opposite Montana, where police seized a cache of guns and ammunition.

"What the operation revealed is that you've got a very small, hardened core driven by ideology," Mr Mendicino said, adding that the nation can no longer tolerate the disruptions and threats.

"We have been fortunate thus far there has not been mass violence," he said.

However, some protesters remain resolute, with one saying after the PM's declaration: "There are no threats that will frighten us. We will hold the line."

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The busiest and most important border crossing, the Ambassador Bridge to Detroit, was reopened on Sunday where a nearly week-long siege had disrupted car production in both Canada and the US.

Ontario premier Doug Ford, whose province includes the site, said the Ottawa siege is complicated by the presence of children in the protest.

"They have kids there. We don't want anything to happen to kids. Bring your kids home," he said.