WASHINGTON, Dec. 4 -- The U.S. National Security Agency is gathering nearly 5 billion records a day on cellphone location data around the world, the Washington Post reported on Wednesday citing the latest leak by former defense Edward Snowden.

The Washington Post's latest report on the agency's intelligence surveillance programs cited top-secret documents provided by Snowden and interviews with U.S. intelligence officials.

The NSA's gathering of the whereabouts of cellphones worldwide has enabled the agency to track the movements of individuals and map their relationships "in ways that would have been previously unimaginable," the newspaper reported.

The NSA uses a powerful analytic tool, known collectively as CO- TRAVELER, to analyze and look for unknown associates of known intelligence targets by tracking people whose movements intersect.

"The NSA cannot know in advance which tiny fraction of 1 percent of the records it may need, so it collects and keeps as many as it can -- 27 terabytes, by one account, or more than double the text content of the Library of Congress's print collection," the newspaper reported.

One senior collection manager, speaking on condition of anonymity but with permission from the agency, told the newspaper that they 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.

In addition, data is often collected from tens of millions of Americans who travel abroad with their cellphones every year, the newspaper reported.

The NSA does not target Americans' location data by design, but the agency acquires a substantial amount of information on the whereabouts of domestic cellphones "incidentally", the newspaper reported.

NSA Director Keith Alexander admitted at a Senate hearing earlier this year that the agency collected some Americans' cellphone location data in bulk as a part of a secret pilot program in 2010 and 2011.