The message prompted most to leave City Hall voluntarily, but a group was arrested.
The chief of guards emphasizes that everything went quietly and peacefully.
According to Ekstra Bladet, nine people were arrested. They are all released again.
The activists come from the popular movement Extinction Rebellion and the group Embassy of the Species Copenhagen. Among other things, they are angry about a controversial construction on Amager Fælled, writes Ekstra Bladet.