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

Denmark summoned the top U.S. diplomat in the country for an explanation following a Wall Street Journal report about the United States stepping up its intelligence gathering on Greenland, a semi-autonomous Danish territory coveted by President Donald Trump.