Several hundred people have staged a protest at a suspected American surveillance facility near Frankfurt in Germany.
Demonstrators held up fake cameras in a symbolic gesture against the heavily secured military complex which allegedly houses a snooping facility of the National Security Agency (NSA).
One protester wore a helmet bearing the phrase “democracy is watching you”.
Police spokeswoman Andrea Loeb said some 450 protesters turned out for the rally at a site nicknamed the Dagger Complex on the outskirts of the town of Griesheim.
Allegations by US whistleblower Edward Snowden about the NSA’s wide-ranging spying activities targeting data and phone communication worldwide have caused concern in Germany, where protecting personal data is an especially sensitive topic.
German Chancellor Angela Merkel has come out strongly in favour of an international agreement to protect electronic data, following revelations about the US surveillance programme PRISM.
“We should be able, in the 21st century, to sign global agreements,” Ms Merkel told the weekly newspaper Welt am Sonntag.
“If digital communication raises new questions worldwide, then we should take up the challenge. Germany is working for that,” she said.
Ms Merkel, who faces re-election in September 22 elections, has been under pressure for weeks to come clean with voters on what she knew about the US online surveillance.
A new poll suggests the snooping affair is not yet a major election issue – but the opposition hopes this will change while the media are turning increasingly hostile.
The issue is sensitive for Ms Merkel, who said last week she only learnt about the scope of the NSA snooping through media reports.
Many Germans are angry that their emails, phone calls, web searches and other data have been captured and stored under the NSA programme.
Protecting personal data is an especially sensitive topic in Germany because of abuses by communist East Germany’s secret police, the Stasi, and the Nazis’ Gestapo.
France is among other countries where concerns have been expressed over alleged snooping by American security agents.
Snowden, whose passport has been revoked by Washington, has been marooned in Moscow airport’s transit zone for the past few weeks, as he seeks asylum in a bid to evade US espionage charges for his leaks.