Germany's foreign ministry says the U.S. ambassador in Berlin has been summoned following the arrest of a German reported to have spied for the United States.
The ministry said in a statement that Ambassador John B. Emerson was asked Friday by a senior German official to assist in the "swift clarification" of the case.
Federal prosecutors said a 31-year-old German man was arrested Wednesday on suspicion of spying for foreign intelligence services. They did not identify the suspect or the intelligence services.
But German media, citing unnamed government sources, reported that he worked for Germany's foreign intelligence service and had admitted to have passed on information to U.S. agents since 2012.
The U.S. National Security Council declined to comment on the case.