Germany summoned the US ambassador in Berlin following the arrest of a man reported to have spied for the United States, heightening friction between the two countries over alleged US eavesdropping in Germany.
US Ambassador John Emerson was called in "in connection with an investigation by the federal prosecutor", the German Foreign Ministry said. The US envoy "was asked to help in the swift clarification" of the case, the ministry added.
The German Federal Prosecutor's office said a 31-year-old man had been arrested on suspicion of being a foreign spy, but it gave no further details. Investigations were continuing, it said. Two lawmakers with knowledge of the affair said the arrested man was an employee of Germany's BND foreign intelligence agency.
The case risks further straining ties with the US, which were damaged by revelations last year of mass surveillance of German citizens by the US National Security Agency, including the monitoring of Chancellor Angela Merkel's mobile phone.
The man, who is German, has admitted passing to an American contact details about a special German parliamentary committee that was set up to investigate the spying revelations made by former US intelligence contractor Edward Snowden, the politicians said.
Both lawmakers are members of the nine-person parliamentary control committee, whose meetings are confidential, and which is in charge of monitoring the work of German intelligence agencies. The parliamentary committee investigating the NSA affair also holds some confidential meetings.
"This was a man who had no direct contact with the investigative committee. ... He was not a top agent," said one of the members of parliament, who spoke on condition of anonymity. The suspect had offered his services to the United States voluntarily, the source said.
Merkel's spokesman Steffen Seibert said: "We don't take the matter of spying for foreign intelligence agencies lightly."
Germany is particularly sensitive about surveillance because of abuses by the Stasi secret police in communist East Germany and by the Nazis. The US embassy in Berlin, the State Department in Washington and the White House all declined to comment.
Bild newspaper said the man had worked for two years as a double agent and had stolen 218 confidential documents.
He sold the documents, three of which related to the work of the committee in the Bundestag, for €25,000 (HK$264,000), Bild said, citing security sources.
Martina Renner, a member of the opposition Left Party on the parliamentary panel, said the case indicated that anyone who examined Snowden's revelations in detail was subject to scrutiny by US intelligence agencies. "If the media reports (about the case) are confirmed then there can't just be a legal response. There also has to be a political response," she said.
Associated Press, Reuters