The National Security Agency tracks the locations of nearly 5 billion cellphones every day overseas, including those belonging to Americans abroad, The Washington Post reported Wednesday.

The NSA inadvertently gathers the location records of 'tens of millions of Americans who travel abroad' annually, along with the billions of other records it collects by tapping into worldwide mobile network cables, the Washington Post said in a report on its website.

Such data means the NSA can track the movements of almost any cellphone around the world, and map the relationships of the cellphone user.