European leaders have pressed the US and Denmark over spying allegations
The allegations state that the two countries collaborated to spy on European leaders, including German Chancellor Angela Merkel.
From 2012 to 2014, Denmark's Defence Intelligence Service (FE) worked with the US National Security Agency (NSA) to gather information, according to Danish broadcaster DR.
Trine Bramsen, Denmark's defence minister, did not confirm or deny the news, but told AFP that "systemic eavesdropping of close allies is unacceptable." During the suspected espionage, she was not in charge of the ministry.
Other officials from Germany, France, Sweden, and Norway were reportedly subjected to surveillance. These countries have also demanded answers.
"It's unfair if countries with close allied cooperation feel the need to spy on one another," Norwegian Prime Minister Erna Solberg told public broadcaster NRK.
Both FE and the NSA are yet to comment.