BERLIN, Oct. 24 (Xinhua) -- The German Foreign Ministry summoned the U.S. ambassador for talks on Thursday as German politicians voiced outrage at alleged U.S. spying on mobile phone communications of Chancellor Angela Merkel.
German Foreign Minister Guido Westerwelle met U.S. Ambassador to Germany John Emerson on Thursday "to make clear the incomprehension and anger of the German side of the reported eavesdropping activities among closest partners," German news magazine Der Spiegel quoted foreign ministry sources as saying.
Merkel also spoke out personally on Thursday after issuing an unusual sharply-worded statement through her spokesperson. "Spying among friends -- that's totally unacceptable," she said before the EU summit in Brussels on Thursday.
German Defense Minister Thomas de Maiziere told ARD television that he had long suspected that his cellphone was being monitored, but never thought it could be the Americans.
"The Americans are and remain our best friends, but this is just not okay," he said, calling for an immediate stop of such practices by U.S. intelligence.
Some German politicians even called into question the continuation of the European Union's free-trade talks with the United States, which started in July.
Social Democratic Party leader Sigmar Gabriel said it was hard to imagine clinching any free trade agreement with the U.S. when the country endangered liberties of citizens, adding it was time for a clear-cut European response to the surveillance scandal of the U.S. intelligence.
Thomas Oppermann, who co-chaired a parliamentary committee overseeing the country's intelligence service, also warned that the EU-U.S. free trade talks could be affected unless the spying allegations are cleared up.
Katja Kipping, leader of German Left Party, called for the establishment of a parliamentary inquiry committee to look into the the NSA wiretapping scandal.
"The days of cover-up is over," she told the German daily Die Welt. "A lot remains to be clarified, also on this side of the Atlantic."
Germany's Federal Prosecutors' Office, which is responsible for crimes against national security, said on Thursday it had launched a so-called "observation process" to seek deeper insight of the spying allegations. The process could lead to a formal investigation.
Berlin's frustration followed outrage in France, after French President Francois Hollande asked for an explanation from his U.S. counterpart Barack Obama earlier over allegations that the U.S. had collected tens of thousands of French phone records between December 2012 and January 2013.