German Interior Minister Hans-Peter Friedrich, who visited the White House on Friday, said he was given assurances that Prism, the surveillance system run by the US National Security Agency (NSA), was "very strictly" limited to tracking terrorism, weapons proliferation and organized crime.

Friedrich met with US Vice President Joe Biden, Attorney General Eric Holder and President Barack Obama's chief counterterrorism advisor, Lisa Monaco. The interior minister disclosed no details on Prism, nor on how much the NSA had eavesdropped on private data of German citizens and what data routes to and from Germany had been tapped.

Watch video 01:25 Share Spying scandal Send Facebook google+ Whatsapp Tumblr linkedin stumble Digg reddit Newsvine Permalink https://p.dw.com/p/196Kk Germany wants US answers over spying

Experts from German ministries and intelligence services would be provided with information on Prism through a US declassification process, he said.

Ahead of Germany's federal election on September 22, the issue triggered by the US whistle-blower Edward Snowden has grabbed headlines in Germany, where memories remain of repression by the Stasi secret police in former East and by the Gestapo during Hitler's Nazi regime.

Friedrich: 'Not acceptable'

Asked by reporters in Washington whether the NSA has broken the law, Friedrich replied: "I clearly told the American friends that we could not accept it, if the NSA had violated laws in Germany."

He added that "quick and easy answers would not be forthcoming, and if there are answers, possibly only those which can be elaborated upon at secret service level."

"The most important aspect was, that all discussion partners here in the United States understand that in Germany and in Europe there is a high level of sensibility about protecting the private sphere and freedoms," Friedrich said. "That message has reached the American colleagues."

'Don't trivalize,' says Gabriel

Earlier on Friday, the chairman of Germany's center-left Social Democrats, Sigmar Gabriel, had told the public broadcaster Deutschlandradio Kultur that Friedrich should "not trivialize" the surveillance issue and should avoid empty "show talks" at the White House.

The question, said Gabriel, was whether 500 million emails per month were being scanned "with the knowledge of the German government and with the involvement of German intelligence services.?

"That is forbidden; that is a criminal act; that is a violation of Article 10 of our constitution. And, I find that one should not play this down," Gabriel said.

If the US secret services also eavesdropped on the EU Commission in Brussels, then that had nothing more to do with combating terrorism, Gabriel added. "Then it simply amounts to economic espionage."

Gabriel's remarks stemmed from documented claims made by Snowden and reported by outlets such as Britain's Guardian newspaper and the German news magazine Der Spiegel that the NSA kept tabs on masses of phone calls, emails and mobile phone messages in the EU's largest economy.

Alarm sounded by data privacy commissioner

Federal data protection commissioner Peter Schaar warned German users of online services provided by the US company Microsoft that the NSA could be spying on their private messages.

Schaar was reacting to a report by the Guardian on Friday that Microsoft had cooperated with the NSA by allowing access to emails on several portals before messages were encrypted.

US law allowed interception of communications data on a "very wide scale" and without prior judicial approval for the targeting of named suspects, Schaar told Bavarian BR public broadcasting.

ipj/rc (AFP, Reuters, dpa)