Mohammed Shabir Ali is accused of possessing a document written by American-born Anwar al Awlaki, who was killed last year in a drone strike after leading al-Qaida in the Arabian Peninsula.
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If no agreements are reached, the idea is for Germany then to begin turning back migrants.
Supporters have been taking trains, planes and automobiles – and even bikes – to get to England’s first match in Volgograd.
Officers were seen taking photographs of graffiti as part of their inquiries.