The U.S. National Security Agency has been covertly collecting mobile phone location data worldwide to the tune of nearly 5 billion records per day, top-secret surveillance documents supplied by whistleblower Edward Snowden have revealed.

Published in the Washington Post the latest classified files point to an enormous NSA database codenamed FASCIA, which contained trillions of device-location records collected from a variety of sources and enabled the U.S. intelligence community to track the actual movements of individuals in other countries and map their relationships “in ways that would have been previously unimaginable.”

The surveillance capabilities outlined in the documents exposed this week are different from a range of other spying programmes described since June 2013, when the Washington Post, the UK Guardian newspaper and several others worldwide including The Hindu in India, began publishing details of the NSA’s activities, as supplied by Mr. Snowden, the former NSA contractor who has won temporary asylum in Russia.

The Post quoted one NSA Senior Collection Manager saying, “We are getting vast volumes” of location data from around the world by tapping into the cables that connect mobile networks globally and that serve U.S. cellphones as well as foreign ones.

While numerous government officials including Robert Litt, General Counsel for the Office of the Director of National Intelligence (DNI), which oversees the NSA, said that all spying programmes collecting location data are “lawful and intended strictly to develop intelligence about foreign targets,” the Foreign Intelligence Surveillance Act that governs such activities only bars snooping on American citizens.

Far fewer restrictions, if any, apply to the NSA’s surveillance of foreigners, and in the most recent expose it was made clear that the FASCIA contained foreign-based data on cell-phone Location Area Code, Cell Tower ID, Visitor Location Register, the unique

IMEI serial number of the handset, the unique IMSI serial number of the user or SIM card and the globally unique MSISDN number indicating the country a device was activated in, its provider and phone number.

Following the string of exposés in the media on the NSA’s mass global surveillance, protests by leaders of foreign governments and privacy rights activists led to intelligence community heads such as NSA chief Keith Alexander and DNI James Clapper being grilled by the U.S. Congress on whether laws had been flouted by the NSA.

India, which was among the surveillance targets of the NSA including its diplomatic posts in Washington and New York, was this week said to have re-upped its discussions with the U.S. on this matter.