Classified files leaked to Danish media suggest some EU states are allowing US spies to install surveillance equipment on cables in order to intercept the emails, private phone calls, and Internet chats of their citizens.

Large amounts of data are said to be swept up via a programme codenamed "RAMPART-A", according to documents disclosed by former US agent Edward Snowden and made public on Wednesday (18 June) by Dagbladet Information and The Intercept.

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Allegations had previously surfaced that member states collaborate to some extent with the US-led surveillance outfit, the National Security Agency (NSA).

At least 15 member states have some sort of partnership with the NSA, according to former Guardian journalist Glenn Greenwald.

Australia, Canada, New Zealand, and the UK have a more robust “Five Eyes” surveillance pact with the Americans.

But the Danish revelations suggest the extent of the collaboration with member states outside the Five Eyes pact is far greater than originally thought.

The NSA documents under RAMPART-A say “foreign partners provide access to cables and host US equipment.”

The equipment allows the Americans to hoover up some three terabits of data every second from the cables.

The documents reveal the NSA has set up at least 13 RAMPART-A sites. Nine are said to have been active last year.

Among the reportedly willing “foreign partners” are Denmark and Germany.

Ryan Gallagher at The Intercept says the two governments “appear to be associated with RAMPART-A because it is the only NSA cable-access initiative that depends on the cooperation of third-party partners.”

German authorities last year spoke out against allegations the Americans had tapped German chancellor Angela Merkel’s mobile phone.

Merkel later floated the idea of creating a “no-spy” pact with Germany on the model of its Five Eyes alliance, but the Americans were not in favour.

The EU also backed down from scrapping a data-sharing agreement with the US known as Safe Harbour.

On Wednesday, the Irish high court in Dublin asked the European Court of Justice to rule on Facebook’s reported ties and co-operation with NSA filed by an Austrian privacy campaigner.

The spy scandal ignited by Snowden’s revelations last year may surface once again in discussions among EU leaders at summit in Brussels next week.

The EU’s data protection supervisor Peter Hustinx on Thursday urged EU heads of state to make a strong commitment to ensure the privacy of their citizens, reports Reuters.

“The allegations of mass surveillance by security services have rocked the trust in the ability and willingness of governments and businesses to protect individuals' personal information,” he wrote in a letter addressed to EU Council chief Herman Van Rompuy.