Police quietly arrested dozens of protesters who crossed a barricade in front of the Peace Tower on Monday.
Several hundred people milled in front of police barriers on the Parliament Hill lawn as a protest against the Keystone XL pipeline.
The arrests came as orderly lines of about six or seven at a time approached the first of the barricades, a waist-high fence. One by one, they used a small stool to step across and then sat on the lawn, while police interviewed them. They were led away at intervals.
Among the first to be cuffed with plastic ties were Dave Coles, president of the Communications, Energy and Paperworkers Union and veteran activist Maude Barlow.
Native drums sounded as the protesters moved forward. At one point, a wheelchair and its occupant were manhandled over the fence.
The demonstration was organized by Greenpeace and other groups who say the 2,700-kilometre pipeline from Alberta to Texas is harmful to the environment in both Canada and the United States.
Protesters waved signs condemning the oil sands: "Ethical oil? That's snake oil. Guaranteed," said one. "Think outside the barrel. Stop the tar sands," read another.
The rally was billed as peaceful and non-confrontational, but police were out in force. They handed out flyers with maps, telling protesters where they can and cannot go and outlining their rights, their limits and police duties.
The protest included members of first nations.
Clayton Thomas-Muller, an aboriginal organizer, said the Assembly of First Nations and the National Congress of American Indians formally came out against Keystone earlier this month.
He said they are upset about the lack of consultation and destruction of hunting and fishing areas, water, air, sacred lands, tribal sovereignty and lack of government monitoring. They want oil-sands development to slow down until government regulation can catch up.
They see higher cancer rates in communities near oil-sands, as well as tumours in the moose, inedible fish, and oily beaver dams.
"It's a really tragic situation," Mr. Thomas-Muller said.
Patricia Warwick, who was arrested at a similar protest in Washington recently, said about 250 people showed up at obligatory civil disobedience training on Sunday.
Ms. Warwick said the message on Parliament Hill is different from the one in Washington because the pipeline has already been approved in Canada.
"My concern is climate change," she said. "The fossil-fuels industry has far too much influence. We have to take it seriously."
Protester Ken Billings said the demonstrators have to risk arrest to get the attention of industry and government.
"We have to take it up a notch," he said. "It's all going to be peaceful. Our side will be non-violent."
The demonstration was inspired by two weeks of protests at the White House, where more than 1,000 people were arrested, including movie star Daryl Hannah.
Already the plans for a sit-in have had a polarizing effect, with both Prime Minister Stephen Harper and Natural Resources Minister Joe Oliver making a point of defending the pipeline late last week – amid a flurry of media releases and news conferences denouncing the pipeline project.
Ottawa has already approved the Canadian portion of the massive pipeline, and officials are lobbying hard for American approval.
The pipeline will pass through six different states, and state governments are holding hearings into the safety of the pipeline this week. The U.S. State Department says it will give the final say by year's end.
Since Canada has already signed off on the $7-billion project, today's demonstration is being pitched as a protest against the oil sands more generally, said Greenpeace organizer Mike Hudema.
The aim, he said, is "to get the government to turn away from the very devastating and very toxic tar sands industry, and to start addressing one of the greatest crises of our time, which is the climate crisis that is currently affecting and displacing millions of people around the world."
Oil companies and the federal government argue that thousands of jobs and millions of dollars of tax revenue are generated by oil-sands activity.
The Canadian Association of Petroleum Producers has enlisted the support of Patrick Moore, a co-founder and former leader of Greenpeace, in a campaign in support of the oil sands.
Mr. Moore says the oil companies are doing a good job in restoring lands once the oil sands have been mined.
"Evidence shows the land will be reclaimed as thriving ecosystems after oil sands are developed to help meet the world's growing energy needs," he said in an association news release.
But the activists counter that the oil sands produce inordinate amounts of greenhouse gases, harm the air and the water, destroy traditional hunting grounds and threaten wildlife. They say government support would be more efficient if it were put toward renewable energy.