Tens of thousands of protesters have marched through the chilly Danish capital and nearly 1,000 were detained in a mass rally to demand an ambitious global climate pact, just as talks hit a snag over rich nations' demands on China and other emerging economies. The mostly peaceful demonstrations in Copenhagen on Saturday 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 their numbers at 40,000, while 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 UN climate conference is being held. There have been a couple of minor protests over the past week, but Saturday'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, masking their faces, threw cobblestones through the windows of the former stock exchange and Foreign Ministry buildings. A police officer received minor injuries when he was hit by a rock thrown from the group and one protester was injured by fireworks, police spokesman Flemming Steen Munch said. Earlier, police said they had detained 19 people, mainly for breaking Denmark's strict laws against carrying pocket knives or wearing masks during demonstrations. At the talks, the European Union, Japan and Australia joined the US 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, told The Associated Press that "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 No. 5 greenhouse gas polluter - will 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 to 25 percent by 2020. "National interest trumps everything else," Ramesh told the AP. "Whatever I have to do, I've said in my Parliament. We'll engage them (the US and China). I'm not here to make new offers." China has made voluntary commitments to rein in its carbon emissions but doesn't want to be bound by international law to do so. In China's view, the US and other rich countries have a heavy historical responsibility to cut emissions and any climate deal in Copenhagen should take into account a country's level of development. Alden Meyer of the Union of Concerned Scientists told the AP that rich nations are trying to re-negotiate 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 goal posts. And developing countries are not going to agree to that, no matter how loudly the rich countries demand it." The tightly focused negotiating text was meant to lay out the crunch themes for environment ministers to wrestle with as they prepare for a summit of some 110 heads of state and government at the end of next week. U.S. delegate Jonathan Pershing said the draft failed to address the contentious issue of carbon emissions by emerging economies. "The current draft didn't work in terms of where it is headed," Pershing said in the plenary, supported by the European Union, Japan and Norway. But the EU also directed criticism at the US, insisting it could make greater commitments to push the talks forward without stretching the legislation pending in Congress. Both the US and China should be legally bound to keep whatever promises they make, Carlgren said. Thousands also marched in a "Walk Against Warming" in major cities across Australia and about 200 Filipino activists staged a festive rally in Manila to mark the Global Day of Action on climate change. Dozens of Indonesian environmental activists rallied in front of the US Embassy in Jakarta. Environmentalists staged stunts and protests in 100 piazzas across Italy, from Venice's St. Mark's Square to a historical piazza in downtown Rome. They carried banners that read "Stop the Planet's Fever" and asked passers-by to sign a petition calling on world leaders to reach a deal to reduce emissions. In Copenhagen, Archbishop Desmond Tutu, a Nobel Peace laureate, and Greenpeace leader Kumi Naidoo were among those ratcheting up the pressure for a fair, ambitious and binding treaty. Naidoo exhorted politicians to act bravely by crafting a fair, ambitious and binding treaty, so they can later "look their children and grandchildren in the eyes" and tell them they did the right thing. "Failure to do so will be the worst political crime that they would have committed," he said. At a candlelight vigil on the conference grounds, Tutu compared the mass demonstrations outside to other popular movements that made a mark in history. "We want to remind you that they marched in Berlin and the wall fell," Tutu said. "They marched in Cape Town and apartheid fell. They marched in Copenhagen and we are going to get a real deal." Demonstrators chanted and carried banners reading "Demand Climate Justice," ''The World Wants a Real Deal" and "There is No Planet B," navigating for miles along city streets and over bridges past officers in riot gear, police dogs and the flashing lights of dozens of police vans. Inside the Bella Center, delegates gathered around flat-screen TVs showing both the larger peaceful rally and the police crackdown on the young activists. Riot police tied them up with plastic cuffs and made them sit down on a closed-off street before busing them to a detention center set up for the climate conference. Britain's Ed Miliband, the climate change secretary, said dealmakers have a long ways to go. "There are difficult issues to overcome," he said, "around emissions, around finance, and around transparency and they are all issues we need to tackle in the coming days." But the climate conference president, Connie Hedegaard, sought to reassure people that world leaders have come to seriously confront climate change. "It has taken years to build up the pressure ... that we're also seeing unfolding today in many capitals around the world," Hedegaard said. "And I believe that that has contributed to making the political price for not delivering in Copenhagen so high."