The diplomatic fallout over allegations the National Security Agency spied on European Union institutions threatened to escalate on Monday as Germany said it was summoning the U.S. ambassador over the breach in trust.
The German government said it wants "trust restored" with the U.S. following reports that American intelligence agencies bugged EU offices.
The German news weekly Der Spiegel reported Sunday that the NSA had bugged EU offices in Washington, New York and Brussels.
The report cited secret U.S. documents allegedly obtained by the NSA leaker and former contractor Edward Snowden.
The European Parliament has demanded an explanation from Washington and warned that EU-U.S. relations could suffer as a result.
German President Angela Merkel's spokesman Steffen Seibert said that if the report was true the U.S. behavior was "unacceptable."
Merkel said the report, if confirmed, demonstrated "Cold War-style behavior." She was said to feel "alienated" over the development.
On Sunday, British newspaper The Independent reported that Germany's Federal Prosecutor's office "was preparing to bring charges against British and U.S. intelligence ... amid fresh allegations that the services spied far more extensively than thought on German phone and internet traffic."
Separately, French President Francois Hollande, Agence France-Presse reported Monday, has requested that the U.S. "immediately stop" spying.
U.S. Secretary of state John Kerry says he doesn't know all the particulars about allegations that the U.S. bugged EU offices. But he says many nations engaged in international affairs undertake lots of different kinds of activities to protect their national interests.
Edward Snowden is still "under the care of the Russian authorities" at Moscow's international airport, according to Ecuadorean President Rafael Correa.