Berlin (AFP) - German authorities said Wednesday they were investigating an alleged foreign spy as reports said the suspect was the second within days believed to be working for US intelligence.
If confirmed, the latest case would further strain transatlantic relations, which have taken a bruising since last year with the NSA surveillance scandal sparked by revelations of fugitive US intelligence contractor Edward Snowden.
"Federal police officers have since this morning searched the residential and office premises of an accused in the Berlin area due to preliminary suspicion of intelligence activities. No arrest has been made," the federal prosecutors office said.
The case was considered "more serious" than that of a German intelligence operative and alleged double agent who was arrested last week on charges of spying for the CIA, said reports by the daily Sueddeutsche Zeitung and two public broadcasters.
Die Welt daily said that the suspect was a German army officer.
The German defence ministry, when asked about the case by AFP, said that "an investigation is ongoing" within the ministry, without elaborating.
The latest case comes hot on the heels of an arrest last week of an unidentified employee of Germany's foreign intelligence agency, the BND.
The man had allegedly sold over 200 documents to the CIA, including information on a German parliamentary panel that has been looking into the Snowden claims and the extent of German cooperation in US snooping.
Chancellor Angela Merkel -- whose mobile phone has been tapped in the past by the US National Security Agency -- has said that the double agent case, if true, would be "a clear contradiction as to what I consider to be trusting cooperation between agencies and partners".
After other German politicians and media also voiced anger, CIA chief John Brennan late on Tuesday phoned Merkel's office and discussed the case with her intelligence services coordinator Klaus-Dieter Fritsche, news website Spiegel Online reported.
The US ambassador to Berlin, John B. Emerson, early Wednesday visited the German foreign ministry for the second time since last Friday, possibly at his own request, national news agency DPA reported.
Foreign Minister Frank-Walter Steinmeier earlier told a German newspaper that "it would be most disturbing if the spying merrily continued while we're looking at the NSA wiretapping activities and have set up a committee in parliament".