The protest followed Trump’s warning on Friday that he “may put a tariff” on countries that oppose his plans to take over mineral-rich Greenland, which is an autonomous territory of Denmark.

They also coincided with a visit to Copenhagen by a bipartisan delegation from the US Congress that has made clear the opposition of many Americans to the Trump administration’s sabre-rattling.

Waving the flags of Denmark and Greenland, the protesters formed a sea of red and white outside Copenhagen city hall, chanting “Kalaallit Nunaat!” – the vast Arctic island’s name in Greenlandic.

Thousands of people have said on social media they would take part in marches and rallies organised by Greenlandic associations in Copenhagen, and in Aarhus, Aalborg, Odense and the Greenlandic capital Nuuk.

“The aim is to send a clear and unified message of respect for Greenland’s democracy and fundamental human rights,” Uagut, an association of Greenlanders in Denmark, said on its website.