"Greenland is not for sale" and "Back off, USA!" it says on some of the banners.
The demonstration is a protest against repeated statements from the USA's President Donald Trump recently that the USA wants to take control over Greenland. The demonstration also coincides with the Vice President JD Vance's visit to Greenland together with his wife.
It is an unacceptable pressure being put on both Greenland and Denmark, believes one of the organizers, Karen Littauer.
We want to show sympathy and show that this is not okay. It is a violation of the worst kind, she says according to the news agency Ritzau.