A total of 43 people were questioned by police, and 40 were later released.

"The demonstrators, who included Greenpeace activists, were not protesting against Obama's visit but against the slow pace of international climate change negotiations," Copenhagen police spokesman Flemming Steen Munch told AFP.

He said the protesters were arrested for unfurling banners or forcing police barricades.

Greenpeace activists unravelled a banner on Sankt Nikolai church in central Copenhagen that read "Obama, right city, wrong date" pressing him to return for the international talks on climate change the city will be hosting.

Obama said he hoped to return to Copenhagen, but did not specify if he would attend the December 7-18 talks, which aim to craft a post-2012 pact for curbing the heat-trapping gases that drive perilous global warming.

The banner was unravelled near Christiansborg castle, where Obama met the Danish royal family and Prime Minister Lars Loekke Rasmussen.

Three Swedes, three Germans, two Finns and one Pole were among the protesters who were released.

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