Frankfurt-based internet exchange provider De-Cix has lost a case against the German international intelligence service (BND) for siphoning off data from its exchanges over a number of years for "intelligence purposes."

The Federal Administrative Court in the eastern German city of Leipzig ruled late Wednesday that the BND was justified in monitoring and recording international telecommunications on the orders of the Interior Ministry.

The court said that De-Cix could even be compelled to help the BND carry out its surveillance of telecommunications.

De-Cix Management GmbH, which is owned by eco Association, the European internet industry body, had filed suit against the interior ministry, which oversees the BND and its strategic signals intelligence.

It said the BND, a partner of the U.S. National Security Agency (NSA), has placed so-called Y-piece prisms into its data-carrying fibre optic cables that give it an unfiltered and complete copy of the data flow.

The surveillance sifts through digital communications such as emails using certain search terms, which are then reviewed based on relevance.

De-Cix said in a statement Thursday that it believed the ruling shielded it from criminal liability for violations of the law protecting German domestic communications against tapping by stating that the German government bore responsibility.

However it said it would review whether it would take its complaint to the Federal Constitutional Court.

Given the mass of daily phone calls, emails, chats, internet searches, streamed videos and other online communications, an effective fire-walling of purely German communications is unrealistic, activists argue.

Germany had reacted with outrage when information leaked by former NSA contractor Edward Snowden revealed in 2013 that U.S. agents were carrying out widespread tapping worldwide, including of Chancellor Angela Merkel's mobile phone.

Merkel, who grew up in communist East Germany where state spying on citizens was rampant, declared repeatedly that "spying among friends is not on" while acknowledging Germany's reliance on the U.S. in security matters.

But to the great embarrassment of Germany, it later emerged that the BND helped the NSA spy on European allies.

Berlin in 2016 approved new measures, including greater oversight, to rein in the BND following the scandal.