Some 300 youths shrouded in black threw bricks and smashed windows as at least 30,000 people protested in Copenhagen yesterday to turn up the heat on world leaders debating global warming.
The rioters, whose faces were also covered, went on rampage in the heart of the city, prompting swift arrests as some 50 policemen in riot gear intervened.
Demonstrators were forced to the ground and then bundled into vans, an AFP reporter witnessed. More than 60 arrests were made, police said, but minor incidents still occurred along the route of the march. Downtown Copenhagen was in virtual lockdown with thousands of police deployed or on standby and helicopters hovering overhead.
The rest of the march - the centrepiece of protests planned in 130 cities across the world - remained peaceful although tension was perceptible as demonstrators condemned the violence, the reporter said.
The city centre was taken over by environmentalists and anti-capitalist demonstrators on a six-kilometre march that would take them to the venue of the ongoing UN conference.
"We put their number at around 30,000 but this is just an estimate," a police official on duty told AFP. The Danish TV2 News channel put the crowd strength between 30,000 and 100,000.
Organisers of the rally had repeatedly urged the crowd to remain calm and friendly before the march began, dominated by calls for social justice and against capitalism.
"Copenhagen is in the eye of the storm. Each year 300,000 people are dying because of climate change. This is not about adaptation, it is about survival," Kumi Naidoo, executive director of Greenpeace International, said in a speech.
Nigerian Nnimmo Bassey, chair of Friends of the Earth International, said, "We cannot allow carbon traders to damage the world. There is no such thing as clean coal or clean crude. Leave the oil in the soil, leave the coal in the hole."
A protester dressed as Santa Claus held up a banner saying warming was occurring twice as fast in the Arctic and that "my Rudolf cannot take it anymore".
Other demonstrators sported banners that read: 'There is no planet B', 'Change the politics not the climate', and 'Nature does not compromise'.
A thorny issue was clearly the responsibility of the bigger polluters to do more to arrest climate change.
Others meanwhile said the bigger nations should not be let off the hook by being allowed to buy carbon credits from other countries.
"It's a question of justice, we must cut carbon emissions at home instead of buying carbon credits elsewhere," said Susann Scherbarth, a 28-year-old German activist from Friends of the Earth.
Danish police had issued a strong warning to potential rioters. "They must not cross certain limits," said police second in command Per Larsen.
Authorities had earlier expelled offenders, deporting two Britons for vandalism and spitting on a police officer and a Frenchman for breaching firearms laws, police commissioner Lars Christian Borg told AFP.