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NSA's mass phone surveillance programme ruled 'unconstitutional'

16 December 2013 Last updated at 23:48 GMT

The National Security Agency's mass collection of telephone data is unconstitutional, a US judge has ruled.

Federal District Judge Richard Leon said the electronic spy agency's practice was an "arbitrary invasion".

The agency's collection of "metadata" including telephone numbers and times and dates of calls was brought to light by ex-NSA contractor Edward Snowden.

Helena Lee reports.