The Danish foreign ministry on Wednesday summoned the top U.S. diplomat positioned in the country over reports that at least three individuals connected to President Trump sought to carry out a covert influence campaign in Greenland.

Trump has repeatedly said that he’s interested in acquiring Greenland, though Denmark has pushed back on the idea of selling the territory. The president has also not ruled out using force to take over the Arctic island.

“We are aware that foreign actors continue to show an interest in Greenland and its position in the Kingdom of Denmark,” Danish Foreign Minister Lars Løkke Rasmussen said in a statement. “It is therefore not surprising if we experience outside attempts to influence the future of the Kingdom in the time ahead.”

“Any attempt to interfere in the internal affairs of the Kingdom will of course be unacceptable,” he continued. “In that light, I have asked the Ministry of Foreign Affairs to summon the U.S. chargé d’affaires for a meeting at the Ministry.”

The public broadcaster, DR, published a report on Wednesday citing unnamed government and security sources who believe that at least three Americans, including two who were said to have previously worked for Trump, traveled to Greenland to try and gather information in order to influence the territory.

DR reported that two individuals tried to cultivate relationships with politicians, businesspeople and locals.

The outlet also wrote that one of those individually was allegedly tasked with compiling a list of Greenlanders who are friendly to the U.S. and a list of those who oppose Trump. They also reportedly got locals to reveal cases that could be used to cast Denmark in a bad light to American media.

DR, which relied on eight sources, said it could not verify whether the Americans were working on their own accord or taking orders from someone else.

The White House did not immediately respond to request for comment.

The Associated Press contributed.