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Protesters with painted faces join a rally outside the Danish parliament in the centre of Copenhagen on Saturday. ((Anja Niedringhaus/Associated Press))

Tens of thousands of protesters marched through the chilly Danish capital and nearly 1,000 were detained Saturday in a mass rally to pressure political leaders to sign a legally binding climate change deal in Copenhagen in the coming week.

Police estimated their numbers at 25,000, while organizers said as many as 100,000 people took part in the march, where delegates from 192 countries began meeting last weekend for the United Nations Climate Change Conference.

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Environment ministers taking part in the conference, including Canada's Jim Prentice, began arriving Saturday in Copenhagen for the second and final week of the talks.

The Copenhagen march was part of a worldwide "Day of Action." The first rallies were held in the Australian cities of Sydney, Melbourne and Adelaide under the banner "Walk Against Warming." Demonstrations also took place in Beijing, New Delhi, Manila and Taipei.

In Copenhagen, the "Day of Action" saw some activists dressed as polar bears or pandas as they walked from the Danish parliament to Cathedral Square in the host city for the 12-day conference. Among the Canadian demonstrators was Toronto Mayor David Miller.

Miller is one of more than 100 mayors from around the world and three from Canada who will convene in Copenhagen next week to talk about what their cities are doing to curb climate change.

'It is embarrassing': Toronto mayor

"I'll tell you — here in Copenhagen everybody's talking about the Canadian government and how it's getting in the way of negotiations," he told CBC News over the phone. "And as a Canadian, it is embarrassing."

He added that Canadian cities aren't sitting and waiting for other governments to act.

"We're acting, we're fighting climate change with policies that create jobs."

Former Irish president Mary Robinson was part of a vigil on the sidelines of the conference.

"It is absolutely vital that we get the messages across to those who have a big responsibility," she said. "This is not an ordinary conference. It's not a conference like a trade conference. Trade conferences can fail; sometimes it's better if they do fail. But this is a conference which mustn't fail."

Mass arrests

As night fell on Copenhagen, police said they rounded up more than 600 people in a preventive action against a group of youths dressed in black at the tail end of the mostly peaceful demonstration.

Industrial countries criticized a draft climate pact Saturday for not making stronger demands on major developing countries.

Initial reaction to the negotiating text submitted Friday underscored the split between wealthy countries and those still struggling to overcome poverty and catch up with the modern world.

Canada has "significant problems" with the draft agreement, according to Michael Martin, Canada's top climate change negotiator. He said delegates should be seeking "a single, legally binding outcome."

The document doesn't specify a solid emission reduction target for developed countries such as Canada, but instead offers a range of options.

For example, the draft calls for emission reductions of 25 to 40 per cent from 1990 levels by 2020 for developed countries.

That is more ambitious than the current climate target outlined by industrialized economies.

With files from The Associated Press