Environmental activists planned a mass act of "civil disobedience" on Parliament Hill on Monday, but a potential standoff instead played out as a polite exchange between demonstrators and police.

The participants said they were willing to risk arrest as they protested against the Keystone XL pipeline extension, but the crowd of about 400 remained peaceful throughout the demonstration.

The issue, which centres on a planned pipeline that will send Alberta oil to refineries near the Gulf Coast in Texas, has been a controversial one in the U.S., attracting criticism from celebrities like Daryl Hannah.

But the "disobedience" in Ottawa amounted to no more than a number of protesters walking up to police barricades, climbing over a stepladder and immediately surrendering to officers.

About 400 people attended the protest, with 100 people being arrested for obstructing police officers, RCMP Sgt. Marc Menard said.

Those who crossed the police barricade were briefly retained with plastic cuffs and then set free after getting $65 fines.

According to Patrick Moore, a former leader of Greenpeace, the turnout shows that the vast majority of Canadians support the oilsands and recognize its importance for the country.

Moore, an ecologist who now operates a public relations company, told CTV News Channel from Vancouver that the Keystone project is the best way to get the oil down to the U.S.

"How else do we get the oil to Texas? Is there a better way? I don't think so," he said.

There has been criticism that the oil should be refined in Canada, but Moore noted that's not the best option. He said that refining the oil in Canada would mean building multiple pipelines to carry the products to the U.S. for export.

"You've got to get the oil where it's needed, and this is the best way to do it."

Moore added that First Nations communities are getting $800 million in contracts from the oilsands, and the industry is also reclaiming mining sites in an effort to return the area to forest.

He blamed the heightened rhetoric about the oilsands on "misinformation" from environmental groups.

"This is all going to be reclaimed, I have seen it all with my own eyes," he said.

Natural Resources Minister Joe Oliver said the project will create "enormous" employment both in Canada and in the U.S.

When asked about criticisms that the oil should be refined in Canada, Oliver said that doing so would not be economically viable, since getting new refineries build would cost up to $20 billion.

"We don't have refinery capacity in Alberta, and it would take two new refineries to process the bitumen … at a cost of between 8 and 10 billion each," he told Power Play.

Earlier, hundreds of police were firmly in place before the demonstration began Monday, which was seen as a pre-emptive strategy against any large protests.

Police handed out flyers to protesters, which spelled out where the participants were allowed to roam, what their rights were and the duties that officers would be performing at the site.

Security appeared keen to avoid anything similar to the December 2009 incident where Greenpeace protesters managed to unfurl a banner from the parliament buildings.

Temporary fences were erected around the parliament buildings on Sunday night.

Environmentalists on both sides of the U.S.-Canada border have spoken out against the pipeline extension, which critics fear could cause a variety of environmental problems if it is constructed.

The Monday protest was expected to be one of the most public rebukes of the pipeline to date, following in the footsteps of another high-profile protest that took place outside the White House last month and involved more than 1,000 people.

However, the Ottawa protest remained tame, with many protesters climbing over a small barricade only to be politely arrested by police.

The rally in Ottawa was organized by Greenpeace and other groups that oppose the Keystone XL pipeline. Other groups involved include the Council of Canadians, the Indigenous Environmental Network and the Polaris Institute.

Liberal Leader Bob Rae made brief mention of the protest during question period in the House of Commons on Monday. Rae used one of his questions to attack the government's record on environmental policy.