Danish police yesterday released hundreds of activists who were detained during a mass rally demanding strong action from delegates at the UN climate conference.

Police said only 13 of the 968 people detained during and after the demonstration in Copenhagen remained in custody last night. Of those, three - two Danes and a Frenchman - were set to be arraigned in court on preliminary charges of fighting with police.

The conference took a day off yesterday, though environment ministers were meeting for informal talks on greenhouse emissions cuts and financing for poor nations to deal with climate change.

The pledges on emissions cuts so far are short of the minimum proposed in a draft agreement to keep temperatures from rising to a dangerous level.

An estimated 40,000 people joined Saturday's mostly peaceful march toward the suburban conference center where the 192-nation UN climate conference is being held.

Riot police detained activists at the tail end of the demonstration when some of them started vandalizing buildings in downtown Copenhagen.

Windows were broken at the former stock exchange and the Foreign Ministry.

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.

The majority of peaceful 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.

Conference President Connie Hedegaard condemned the troublemakers.

"You don't have to exert that kind of violence to be heard because this is a process where your views are very much included," she said.

There were more protests yesterday, but no reports of violence.