Denmark Prime Minister Mette Frederiksen said "you cannot spy against an ally" after reports that the U.S. was gathering intelligence on Greenland.

Danish Prime Minister Mette Frederiksen has issued a stern warning to the Trump administration following reports that U.S. intelligence agencies have been ordered to increase surveillance efforts targeting Greenland.

The Denmark prime minister's comments come a day after the top American diplomat in the country was summoned for an explanation of reports of U.S. intelligence gathering in Greenland.