Britain's Guardian newspaper reports that spy agencies across Western Europe are working together on mass surveillance of Internet and phone traffic.

Citing documents leaked by Edward Snowden, the Guardian said spy methods included tapping into fibre optic cables and working covertly with private telecommunications companies.

The Guardian named Germany, France, Spain, Sweden and the Netherlands as countries where intelligence agencies had been developing such methods in cooperation with counterparts including Britain's surveillance agency GCHQ.

The Guardian says files leaked by Snowden showed the British agency taking credit for advising European counterparts on how to get around domestic laws intended to restrict their surveillance powers.