Screenshot from video purportedly showing Boko Haram leader Abubakar Shekau and militants - file image
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US brands Nigeria's Boko Haram and Ansaru 'terrorists'

13 November 2013 Last updated at 20:51 GMT

The US has designated Nigeria's Boko Haram and Ansaru militant groups as foreign terrorist organisations.

The state department described the move as "an important" step to help Nigeria "root out violent extremism".

The BBC's Will Ross reports.