TORONTO -- Climate change activists Extinction Rebellion have organized a series of protests to block busy bridges to traffic across Canada.

The environmental campaigners, known as XR, seek to draw attention to the “climate emergency” and want to achieve net zero carbon emissions by 2025.

It plans to shut down some of Canada's busiest bridges on Monday, in line with protests around the world; including the Angus L. Macdonald Bridge over Halifax Harbour, the Burrard Street bridge in Vancouver and the Prince Edward Viaduct in Toronto, by having protesters lie down or sit in traffic lanes, according to The Canadian Press.

Halifax’s Macdonald Bridge was closed to vehicle, pedestrian and bike traffic for around four hours on Monday morning as fewer than 100 XR members gathered for a protest, CTV News Atlantic reports.

The demonstration forced some commuters to take alternate routes to work and fueled congestion on main arteries throughout Halifax and Dartmouth.

CTV News Atlantic reported 18 protesters had been arrested by around 11.30 a.m. ET.

Police initally said they arrested 14 protesters under the Protection of Property Act for failing to leave the premises after being ordered to do so. They later corrected that number to 18 arrests.

The bridge was closed to traffic just before the protesters arrived on scene and police blocked their access to the bridge.

About 40,000 vehicles use the Macdonald bridge daily along with about 1,200 people who bike or walk across the span. The bridge was reopened to traffic by midday.

"I think this is a huge success," protest organizer Patrick Yancey told The Canadian Press just moments before he was arrested.

"I think it's going to be great for the whole world to see all of the people who are willing to make this sacrifice in order to get some action on this climate crisis."

In Toronto, dozens of protestors shut the Prince Edward Viaduct connecting a main road in the east of the city to downtown Toronto. The demonstration, which was due to finish at 10 a.m. ET, still had protesters in place by 11.30 a.m.

Police told The Canadian Press they made 20 arrests at the end of the demonstration, but said the protests were peaceful.

XR organizer in Toronto, Kevin Imrie, said people were arrested after a number of protesters refused to disperse.

“We did the best that we could to close things down in an organized fashion,” Imrie told CTV News Channel.

“I understand that people are angry. I would also hope that they would be angry at the folks who are putting them in danger by not taking action on climate change.”

On the other side of the country police in Victoria, B.C., say they are prepared for another XR protest at the Johnson Street Bridge, CTV Vancouver Island reports.

Organizers said the action will close the Johnson Street Bridge to traffic from 3:30 p.m. to 7 p.m.

"The #BridgeOut campaign points out that the bridge to the future is being demolished by big oil, and oily politicians," said a Facebook page organizing the event.

"This escalation of tactics is the minimum of what’s necessary to give young people a fighting chance at a decent future. We regret that ordinary people will be frustrated by the commute disruption, but the collapse of human society would be a much bigger inconvenience."

Protesters also shut the Burrard Street Bridge in Vancouver, where police arrested 10 people late Monday after they refused to leave the bridge linking the city's downtown to the west side.

The four-lane bridge sees about 55,000 vehicles a day.

And in Edmonton, a handful of XR protesters linked arms to block the Walterdale Bridge Monday morning to demand action on climate change.

Alberta Premier Jason Kenney, criticizing the action on Twitter, noted that traffic backups meant hundreds of cars were idling for no good reason.

The police service told The Canadian Press that an officer negotiated with the protesters, who agreed to end the blockade an hour earlier than planned.

No one was arrested, but police said they are investigating and there could still be charges.

The protest in Alberta’s capital was one of 60 happening around the world on Monday under the umbrella #BridgeOut, according to CTV News Edmonton.

Calgary was planning a "family-friendly" event on Monday afternoon, The Canadian Press reported.

A protest slated to take place in Montreal was postponed until Tuesday due to rain.

Meanwhile in London, England, police arrested 21 climate change activists on Saturday and Sunday on suspicion of conspiracy to cause a public nuisance. Further protests took place in London on Monday.

The arrests come as protesters in Berlin and Amsterdam blocked roads ahead of what is being described as widespread demonstrations.

In New York City, protesters doused a famous statue of a charging bull near Wall Street with fake blood.

Last week, XR attempted to spray fake blood on a British government building in London, using an out-of-commission fire engine to drench the front of the Treasury building.

Founded in Britain last year, XR now claims chapters in 50 countries.

---- With files from The Canadian Press and The Associated Press