Hundreds of Islamist protesters have taken to the streets of Zanzibar's Stone Town demanding to know the whereabouts of a local cleric they claim has been detained by police. Islamic Revival Forum leader Sheikh Farid Hadi is an ardent proponent of Zanzibarian secession from mainland Tanzania. His disappearance triggered rioting and looting in the island's historic centre. Masked supporters, some armed with machetes, blocked Stone Town's main road. Traffic and business activity were paralysed for hours as the missing cleric's supporters rampaged through the streets, watched from a distance by police. One officer was killed on his way home from the demonstration according to the island's police commissioner.