The Guardian newspaper says that British spies are running an online eavesdropping operation so vast that internal documents say it even outstrips the United States' international Internet surveillance effort.

The paper cited internal documents from the British spy agency GCHQ to claim that U.K. spies were tapping into scores of fiber optic cables to harvest data, including phone calls and emails.

Fiber optic cables — thin strands of glass bundled together — have been estimated to carry some 95 percent of the world's international voice and data traffic.

The Guardian said Friday that GCHQ is monitoring more than 200 cables, although it did not go into much detail as to their nature, their location, or how they were being tapped.

GCHQ did not immediately return messages seeking comment.