Thousands of protesters gathered in the Danish capital Saturday to demand tough action by world leaders to curb global warming, but hundreds were detained as police tried to quell any potential violence.

Extra police were on hand to monitor the crowd as it marched through the city, beating drums, waving signs and chanting.

Nearly 1,000 protestors were detained by Danish police. But many protesters simply carried signs or dressed in costumes, such as penguins and polar bears.

Organizers estimated that upwards of 100,000 people joined the protests, though Danish police estimate only 40,000 took to the streets.

Police said 968 people were detained as a preventative action against some young activists at the end of the demonstration. Officers wearing riot gear rounded up the activists, when some of them, wearing marks, threw cobblestones through the windows of the former stock exchange and Foreign Ministry buildings.

One officer sustained minor injuries in the operation.

A draft accord, released Friday at the UN climate change talks in Copenhagen, calls for wealthy nations to cut emissions by 20 to 40 per cent by 2020. This would pave the way to reaching a broader goal of reducing worldwide greenhouse gas emissions by a whopping 50 to 95 per cent over the next 40 years.

To achieve both goals, 1990 emissions would be used as the baseline year.

Representatives from industrial nations criticized the pact for failing to address greenhouse gas emissions by emerging economies.

"The current draft didn't work in terms of where it is headed," U.S. delegate Jonathan Pershing wrote in a plenary, supported by the European Union, Japan and Norway.

Swedish Environment Minister Andreas Carlgren told The Associated Press that "there has been a growing understanding that there must be commitments to actions by emerging economies as well."

The statement came as environment ministers from around the globe began arriving in Copenhagen Saturday for informal talks ahead of meetings with 110 world leaders, including Prime Minister Stephen Harper and U.S. President Barack Obama, late next week.

The summit aims to work out an agreement that will reduce greenhouse gas emissions that contribute to climate change and help poor nations deal with the effects of global warming -- from rising sea levels to reduced rainfall.

But it will likely be difficult for participants to agree on the massive financial commitments required for achieving that goal, which some analysts say could amount to US$150 billion per year.

No financial terms were included in the draft. However, it calls for all countries together to reduce emissions by 50 to 95 per cent by 2050.

"It's time to begin to focus on the big picture," Yvo de Boer, the top UN climate official, said Friday. "The serious discussion on finance and targets has begun."

The draft calls for action similar to the 1997 Kyoto Protocol, which legally binds signatories to emission-reduction targets and imposes penalties for failing to meet them.

However, the draft makes no mention of developing countries such as China and India, which have agreed to voluntarily cut emissions but reject the idea of committing to legally binding targets.

The draft also left open the possibility that it could be signed in the form of a political declaration, or a legal document that would bind signatories to targets.

Ian Fry, a delegate of the tiny Pacific island of Tuvalu, choked back tears as he pleaded with leaders to make the targets legally binding.

"I woke up this morning crying, and that's not easy for a grown man to admit," Fry told the plenary. "The fate of my country rests in your hands."

Southern island nations have played a particularly vocal part in the demonstrations as many of the smaller countries have taken the brunt of global warming effects.

"All week we have heard a string of excuses from northern countries to make adequate reparations for the ecological crisis that they have caused," said Lidy Nacpil, of the Jubilee South Coalition. "We are taking to the streets to demand that the ecological debt is repaid to the people of the South."

Across Asia, activists gathered to mark the Global Day of Action on climate change. About 200 protesters demonstrated in Beijing, and another 200 gathered in Manila, while dozens rallied in front of the U.S. embassy in Jakarta.

Thousands of marchers also protested in cities across Australia in a national "Walk Against Warming."

With files from The Associated Press