COPENHAGEN, Denmark - Tens of thousands of protesters marched through the chilly Danish capital and almost a thousand people were detained yesterday in a mass rally to demand an ambitious global climate pact as talks hit a snag over rich nations' demands on China and other emerging economies.

The mostly peaceful demonstrations in Copenhagen provided the centerpiece of a day of global climate activism stretching from Europe to Asia. Police assigned extra officers to watch protesters marching toward the suburban conference center to demand that leaders act now to fight climate change.

Police estimated the number at 40,000, but organizers said as many as 100,000 had joined the march from downtown Copenhagen. It ended with protesters holding aloft candles and torches as they swarmed by night outside the Bella Center, where the 192-nation U.N. climate conference is being held.

There have been a couple of minor protests over the last week, but yesterday's was by far the largest.

Police said they rounded up 968 people in a preventive action against a group of youth activists at the tail end of the demonstration. Officers in riot gear moved in when some of the activists, wearing masks, threw cobblestones through the windows of the former stock exchange and Foreign Ministry buildings.

A police officer suffered minor injuries when he was hit with a rock and one protester was injured by fireworks, police spokesman Flemming Steen Munch said.

Police said earlier that they had detained 19 people, mainly for breaking Denmark's strict laws against carrying pocket knives and wearing masks during demonstrations.

Inside the Bella Center, representatives from the European Union, Japan, and Australia joined U.S. officials in criticizing a draft global-warming pact that says major developing nations must rein in greenhouse gases, but only if they have outside financing. Rich nations want to require developing nations to limit emissions with or without financial help.

Swedish Environment Minister Andreas Carlgren, representing the 27-nation EU, said, "There has been a growing understanding that there must be commitments to actions by emerging economies, as well."

He said those commitments "must be binding, in the sense that states are standing behind their commitments."

Indian Environment Minister Jairam Ramesh said his country - the world's fifth-biggest greenhouse-gas polluter - would not offer more than its current pledge to slow its growth rate of emissions. It has offered to cut greenhouse gases measured against production by 20 percent to 25 percent by 2020.

"National interest trumps everything else," Ramesh said. "Whatever I have to do, I've said in my parliament. We'll engage them [the United States and China]. I'm not here to make new offers."

China has made voluntary commitments to limit its carbon emissions but doesn't want to be bound by international law to do so.

Alden Meyer of the Union of Concerned Scientists said rich nations were trying to renegotiate the deal they reached two years ago on the island of Bali, calling on developing nations to limit emissions with financial help.

"It's going to blow up in their faces," he said. "The rich countries are trying to move the goalposts. And developing countries are not going to agree to that, no matter how loudly the rich countries demand it."