A German security agency has intercepted a call involving Hillary Clinton who holding office as the U.S. Secretary of State at the time, three German news outlets reported on Friday.

According to German broadsheet Sueddeutsche Zeitung and local broadcasters WDR and NDR, the conversation was recorded while Clinton was aboard a U.S. government plane but did not elaborate on who she was talking to or where the call was made.

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The revelation could become a potentially embarrassing matter for Berlin who has continuously denounced Washington's spying activities.

The recording had been "accident" and was in no way part of a plan to spy on Washington's top envoy, said the German broadsheet, citing unidentified government sources.

One source had reportedly said it was "idiocy" that the recording was not immediately destroyed.

Both Germany and the U.S. declined to comment on the matter.

Based on the German news agencies, the details of Clinton's call were included in documents passed on the Washington by Markus R., a former employee of the BND, German's foreign intelligence agency.

Markus R. approached Washington's Central Intelligence Agency in 2012 and passed on sensitive information from the government, Reuters reported.

He was detained by German authorities last month and is under suspicion for passing on information to other countries, including Russia.

Further investigations by the three news agencies revealed that the German government had commissioned the BND to conduct surveillance operations on a NATO state, Reuters has learned.

The news of the recording comes after last year's disclosure by Edward Snowden - a former U.S. National Security Agency contractor - that U.S. government agencies had conducted surveillance operations on German officials, including Chancellor Angela Merkel.

Germany condemned Washington for the espionage, saying that such acts must not be committed among friends.

Tensions reignited after the arrest of Markus R. German officials claimed the U.S. should have never worked with the spy. Shortly after, Merkel had requested the head of the American intelligence in Berlin to leave.

TagsGermany, US, spying, BND, CIA, cyber espionage, Edward Snowden, Markus R.