Large bouquets of flowers have been left by local Malaysians to offer condolences to the families of British students Neil Dalton and Aidan Brunger, who were stabbed to death in Borneo.
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Some 66 people have been killed after the plane they were travelling on crashed in southern Iran.
The letter calls for an end to harassment, abuse, and impunity in a world "ripe for change".
Police say that anyone who sees Whitehouse should not approach him, but instead call them on 999 and quote incident 23 of 18 February.