Scotland Yard is investigating a video apparently made by Somali militant group al-Shabab after British Muslims who have spoken out against extremism were named as targets.
The hour-long film, narrated by an unidentified man with a British accent, reportedly praises acts of Islamist terrorism and starts by hailing the killing of soldier Lee Rigby in Woolwich, south east London.
The video singles out British Muslim commentator Mohammed Ansar as one of those who "distanced themselves" from those who carried out the attacks and as having "mutilated the teachings of Islam", according to reports.
He is one of a number of prominent Muslims to claim police have issued warnings to following credible evidence of potential threats against them.
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