Angela Merkel

BERLIN: German federal prosecutors have opened an investigation into the alleged monitoring of Chancellor Angela Merkel’s cell phone by the U.S. National Security Agency, they said Wednesday.

Chief Prosecutor Harald Range has been mulling for months whether to open a formal probe of the Merkel allegations that emerged in October.

The revelations cooled relations between Berlin and Washington, prompting Merkel to accuse the US of a grave breach of trust and President Barack Obama to pledge he would not allow America’s massive communications surveillance capability to damage relations with Germany or other close allies.

Range’s office said he opened an investigation Tuesday into persons unknown regarding Merkel’s phone, a move that could again complicate matters diplomatically.

“Extensive preliminary investigations have established that sufficient factual evidence exists that unknown members of U.S. intelligence services spied on the mobile phone of Chancellor Angela Merkel,” Range’s office said.

In addition, his office said, prosecutors will continue to monitor the “possible massive collection of telecommunications data of German citizens by British and American intelligence services.” It said they would also intensify their efforts against “cyber-espionage.”