The US National Security Agency is collecting some five billion records a day on the location of mobile phones around the world, The Washington Post reported, citing documents from US intelligence leaker Edward Snowden. The information is added to a gigantic database that shows the locations of "at least hundreds of millions of cell phones" worldwide, a stunning revelation that suggests the eavesdropping agency has created a mass surveillance tool, the report says. Of the NSA surveillance programmes revealed to date, the geo-location project appears to represent the agency's largest in scale and scope. The NSA declined to comment on the report. The data was scooped up by tapping into cables that link mobile phone networks - both American and foreign - across the globe, the Post said. The location data was gathered with the help of 10 "sigads" or signal intelligence activity designators. In an example given by the Post , one sigad called "stormbrew" collects data from two unnamed corporate firms which administer interception equipment. Then the "NSA asks nicely for tasking/updates," according to leaked documents. Information from the phones of Americans travelling abroad also forms part of the database. Because mobile phones broadcast their locations even when there is no call made or text sent, NSA analysts were able to use mathematical techniques to comb through location data and track patterns of movement over time for a given suspect, it said. The analytic methods used by the agency to sift through location data were known as Co-traveler, the report said. Although the vast majority of mobile phone users were of no interest to the NSA, it gathered the bulk data to try to track known "intelligence targets" and their unknown associates, the paper said. Even the use of disposable phones that users switch on and off to make only brief calls in the hopes of avoiding authorities trigger note in the system. The NSA insisted it did not intentionally track the location data of Americans, but it ended up receiving details that showed the whereabouts of domestic mobile devices "incidentally," wrote the Post , which also quoted intelligence officials. US officials told the Post that the programmes that collected geo-location data were legal and designed only to gather intelligence about foreign militants or other "targets" deemed a threat to the United States. The volume of information flowing in from the program was "outpacing our ability to ingest, process and store" data, according to a May 2012 internal NSA briefing leaked to the Post . The scale of the programme will reinforce long-running concerns raised by civil liberties groups that the NSA's electronic spying poses a serious threat to privacy rights worldwide. "It is staggering that a location-tracking programme on this scale could be implemented without any public debate, particularly given the substantial number of Americans having their movements recorded by the government," said Catherine Crump, an attorney with the American Civil Liberties Union.