Hundreds of Islamic radicals set fire to two churches and clashed with police over the weekend on the Muslim-dominated island of Zanzibar, Reuters reports. Christian minorities have repeatedly come under attacks from Islamists in Zanzibar, and the newest attacks have raised fears of an escalation in religious tensions. "There's a lot of tension, people are hiding in their houses," resident Mai Zuberi said. "All the streets are empty; it's only the police who are out there." Police said they have arrested 30 members of Uamsho -- a Swahili acronym of the Association for Islamic Mobilization and Propagation -- but the group dismissed the accusation of inciting riots.