Germany's top public prosecutor has launched an investigation into the bugging of Angela Merkel's mobile phone in the light of revelations that the US National Security Agency had spied on the chancellor, authorities have said.
Attorney General Harald Range's office said on Wednesday that Germany's top federal prosecutor had enough data to push ahead with an official investigation.
"Extensive preliminary investigations produced sufficient factual evidence that unknown US intelligence officers tapped a mobile phone of Chancellor Angela Merkel," said a statement from Range's office.
Although there is not yet a strong enough case to start legal proceedings, Range's office said he was still looking into wider allegations that both US and British intelligence carried out "massive surveillance of the German population's telecommunications data".
Germany and the US have been at odds over the US National Security Agency's (NSA) spying habits since whistleblower Edward Snowden's revelations last year showed the United States had listened in on many of its allies, including Merkel, severely testing ties between Berlin and Washington.
Justice Minister Heiko Maas told German radio earlier in the day that investigators would "have to take action" if it came to light that German law had been broken regarding Merkel's mobile phone or other surveillance revealed by Snowden.
Revelations that the United States and Britain have carried out large-scale electronic espionage in Germany - including from the roofs of their embassies in Berlin, near Merkel's office and the Reichstag - have provoked widespread indignation in Germany.
When Merkel visited President Barack Obama in May, she was asked by reporters if trust had been restored. She replied by saying that "we have a few difficulties to overcome", referring to the conflict over US surveillance practices.
Snowden, who has sought refuge in Moscow, has promised to bring new information to light proving Germany's' rights were violated by American intelligence if he is able to give evidence to a German parliamentary committee investigating the matter.
Merkel's government has so far declined to bring him to Berlin to testify in person fearing it would further damage relations with Washington.
Last October, German magazine Der Spiegel reported that the US may have bugged Merkel's phone for more than 10 years. But the White House has assured the chancellor that her communications are not being monitored after Merkel called Obama to demand a clarification.