Germany’s foreign intelligence service secretly monitored the telephone communications of former U.S. President Barack Obama for several years, including calls made aboard Air Force One, according to an investigation by the German newspaper Die Zeit.

The operation was carried out without the knowledge or authorisation of then-Chancellor Angela Merkel and was halted only in 2014.

The German Federal Intelligence Service (BND) intercepted President Obama’s communications while he was travelling on the US presidential aircraft, exploiting technical vulnerabilities in its encryption, the report said. Insiders told Die Zeit that technicians on Air Force One used multiple frequencies for secure calls, some of which were known to and regularly monitored by the BND, though not continuously.

The surveillance is politically sensitive, as it targeted the leader of a close ally and fell outside the BND’s official mandate, which did not include monitoring the United States. According to the report, the operation was not formally authorised by the German government, and it remains unclear whether officials within the Chancellor’s Office were aware of it. Angela Merkel herself was reportedly not informed and would likely have blocked such an operation had she known.

Transcripts of the intercepted communications were handled under strict internal rules. They were stored in a special folder, produced only in single copies, and circulated among a small group of senior intelligence officials, including the BND president and vice-presidents. After being reviewed, the transcripts were to be destroyed, with key findings later incorporated into broader intelligence assessments shared with the Chancellor’s Office.

The operation reportedly came to an end in 2014, after Süddeutsche Zeitung revealed that then U.S. Secretary of State Hillary Clinton had been wiretapped by German intelligence. Following that disclosure, Peter Altmaier, who was head of the Federal Chancellery at the time, ordered the practice to be stopped, apparently without knowing that the U.S. president himself had also been targeted.

The revelations add a new dimension to the 2013 espionage scandal in which it emerged that the U.S. National Security Agency (NSA) had tapped Merkel’s mobile phone for years. At the time, the chancellor publicly condemned the practice, declaring that “spying among friends is unacceptable”. Privately, she reportedly likened excessive surveillance to the methods of East Germany’s Stasi and warned that states could collapse under its weight.

It remains unclear when the BND’s surveillance of Obama began, or whether his predecessor, George W. Bush, was also monitored. Neither Merkel’s office nor the BND has commented on the allegations.

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