Muslims have clashed with police in Zanzibar in a row over the date of the Muslim festival of Eid - the celebration to mark the climax of the Hajj pilgrimage.
Muslims who started praying in a mosque on Tuesday were interrupted by police who fired tear gas and plastic bullets to disperse them.
The Zanzibar Goverment wants Eid to be celebrated on Wednesday, when the president is due to address the Eid Council.
But Muslims began celebrating Eid on Tuesday, arguing that the moon had already been seen in Saudi Arabia, and the festivities should begin.
Police used weapons against Muslims in the mosque when they refused to stop praying.
Four people were injured in the ensuing fracas.
The BBC's Ali Saleh in Zanzibar said a seriously injured person was being held in police custody.
Six have been charged with contravening the orders of the Mufti, the Muslim authority in the country, and released on bail.
Six months ago a law was passed allowing only the Mufti to decide when Eid should be celebrated.
Our correspondent says that the power struggle between the government and ordinary Muslims has been going on for a long time.
Many say they will not be dictated to in order to be able to celebrate Eid when they want.