Muslim clerics in Zanzibar have blocked a bid by two gay lovers to exchange marriage vows. The discreet ceremony was stopped after reports reached members of the Zanzibar Imams' Propagation Association. Police have arrested four imams who allegedly assaulted the couple. They have also launched investigations with a view to prosecuting the partners. Zanzibar is a predominantly Muslim island, where acts of homosexuality are illegal and few people are openly gay. One of the partners is from Mombasa in Kenya and another from the island of Pemba in the Zanzibar archipelago.