France warned Monday that alleged US spying on European allies using Danish underwater cables would be "extremely serious" if confirmed, as questions mounted over whether Denmark knew what the US was doing.
In an investigative report on Sunday, Danish public broadcaster Danmarks Radio (DR) revealed together with several other European media outlets that the US National Security Agency (NSA) had eavesdropped on Danish underwater internet cables from 2012 to 2014 to spy on top politicians in Germany, Sweden, Norway and France.
The NSA was able to access text messages, telephone calls and internet traffic including searches, chats and messaging services -- including those of Germany's Chancellor Angela Merkel, then-foreign minister Frank-Walter Steinmeier and then-opposition leader Peer Steinbruck, DR said.
"It is extremely serious," France's Europe Minister Clement Beaune told France Info radio.
"We need to see if our partners in the EU, the Danes, have committed errors or faults in their cooperation with American services."
He added it would also be very disturbing if Washington had been spying on EU leaders.
"Between allies, there must be trust, a minimal cooperation, so these potential facts are serious," said the minister.
He said the facts must first "be verified" and then "conclusions drawn in terms of cooperation".
Denmark's neighbours Sweden and Norway have also demanded explanations from Copenhagen, though the tone has been more cautious.
And a German government spokesman said Monday that Berlin was "in contact with all relevant national and international interlocutors to get clarification".
Systematic eavesdropping 'unacceptable'
DR said the NSA had taken advantage of a surveillance collaboration with Denmark's military intelligence unit FE to eavesdrop on the cables.
But it was unclear whether Denmark knew at the time that the US was using the cables to spy on Denmark's neighbours.
Contacted by AFP, FE refused to comment on the revelations.
Defence Minister Trine Bramsen, who took over the defence portfolio in June 2019, has neither confirmed nor denied DR's report, telling AFP only that "systematic eavesdropping of close allies is unacceptable".
US eavesdropping on European leaders is, however, not new.
In 2013, former NSA contractor Edward Snowden revealed thousands of classified documents exposing the vast US surveillance put in place after the September 11, 2001 attacks.
Among other things, the documents showed the US government was spying on its own citizens and carrying out widespread tapping worldwide, including of Merkel's mobile phone.
However, if the Danish-US spying is confirmed, it went on during and after the 2013 Snowden affair.
In 2014, following the Snowden scandal, a secret internal working group at FE began looking into whether the NSA had used a Danish-US spying collaboration -- called XKeyscore -- to spy on Denmark's allies, DR said.
The group's report, codenamed Operation Dunhammer, was presented to top FE management in May 2015.
What happened after that is not yet known.
'New pieces of the puzzle'