Police arrested almost 1,000 people among the violent fringes of a mass rally in Copenhagen intended to put pressure on the UN climate summit to take stronger action.

Tens of thousands of people took part in the Saturday march to the heavily guarded conference centre where world powers are struggling to hammer out a deal to combat global warming. Other rallies were held around the world from Australia to the Arctic Circle.

Most of the main Copenhagen rally was peaceful, but police moved in when hundreds of youths clad in black threw bricks and smashed windows. Riot police surrounded the troublemakers and made them sit on the ground with their hands behind their backs before being taken away on buses.

Police made 968 arrests, including about 400 members of militant groups from across Europe known as Black Blocs. About 150 were released after questioning.

Demonstrations were also held in Australia, Indonesia and the Philippines demanding tough measures by the 194 nations gathered at the UN Framework Convention on Climate Change (UNFCCC) conference.

The summit is due to end on Friday with a gathering of more than 110 heads of state and government to seal a deal committing major economies to curb emissions of heat-trapping fossil-fuel gases and generate hundreds of billions in dollars for poor countries badly exposed to climate change.

Connie Hedegaard, a former Danish climate minister chairing the summit said world leaders must not resist the global clamour.

"It has taken years to build up pressure that we see around the world, and that we have also seen unfolding today in many capitals," Hedegaard said.

The Copenhagen march capped demonstrations in some 130 cities around the world, including Washington, where protestors erected a mock Noah's Ark to warning leaders that the planet faces a crisis of biblical proportions.

But many delegates at the summit complained that progress so far had been negligible and the mood soured by finger-pointing.

A seven-page draft blueprint, presented on Friday, ran into problems almost immediately among developing countries, emerging giant economies, the United States and the European Union.

Poor countries said it failed to spell out financial commitments while the United States complained it failed to bind China and other high-population, fast-growing economies to tough pledges on emissions.

The European Union said the draft did not go far enough to limit warming to two degrees Celsius (3.6 degrees Fahrenheit), a goal endorsed by many countries.

"We are in a situation where we can see that so far we haven't achieved enough," Andreas Carlgren, environment minister of Sweden, which currently chairs the 27-nation European Union.

The European Union has unilaterally decided to cut greenhouse-gas emissions by 20 percent over 1990 levels, and has offered to deepen this to 30 percent if it finds other major players willing to make a comparable effort.

But Carlgren ruled this out, blaming foot-dragging by the world's top two carbon emitters.

"So far we haven't sufficient bids on the table," he told a press conference. "So far the bids from the United States and China are not sufficient whereby we can deliver this 30 percent."

Environment ministers from 48 countries were to meet through the weekend to discuss measures.

"We still have a daunting task in front of us over the next few days," she said.

This weekend's meetings mark the start of a gruelling game of climate poker before the arrival of heads of state and government on Wednesday and Thursday, many of whom will speak in the conference's plenary session.

Those rostered to attend include US President Barack Obama, Russian President Dmitry Medvedev, Chinese Premier Wen Jiabao, Indian Prime Minister Manmohan Singh, Brazil's President Luiz Inacio Lula da Silva, Prime Minister Yukio Hatoyama of Japan, and the heads of the European Union.

Failure this coming Friday would deal a heavy blow to the nation-state system, Rajendra Pachauri, the head of the United Nations' Nobel-winning panel of climate scientists, warned on Saturday.

"I think if we are able to get a good agreement, this would clearly create an enormous amount of confidence in the ability of human society to be able to act on a multilateral basis," said Pachauri, chairman of the Intergovernmental Panel on Climate Change (IPCC).

"If we fail, I don't think everything is lost, but certainly it will be a major setback."