By Munir Zakaria

STONE TOWN, Zanzibar (Reuters) - Seven leaders of a separatist Islamic group seeking to free the semi-autonomous island of Zanzibar from Tanzania were charged with incitement to violence on Monday, while police fired teargas on their supporters outside the court.

The Islamic group Uamsho (Awakening) is pushing for the predominantly Muslim island's exit from its 1964 union with mainland Tanzania, which is ruled as a secular country.

Muslim protesters clashed with police in Tanzania's commercial capital and on the semi-autonomous island of Zanzibar on Friday, raising religious tensions in east Africa's second-biggest economy.

Police fired teargas in Zanzibar's capital, Stone Town, to disperse members of the group who gathered outside the court to witness the arraignment of their leaders. The officials of the group were charged with causing riots on the island in August.

"Leaders of the Uamsho group were charged with inciting the previous violence that occurred in Zanzibar in August. They have not been immediately charged with last week's riots," Zanzibar police spokesman Mohamed Mhina told Reuters.

The mostly youthful supporters and urban poor fought police in running street battles for three days last week after Sheikh Farid Hadi, one of Uamsho's spiritual leaders, disappeared in unknown circumstances on Tuesday.

Hadi said policemen with balaclavas blindfolded him and took him to an unspecified location to interrogate him about Uamsho's plans for Zanzibar and activities in Middle Eastern countries.

"All they wanted to know was what we are trying to do now and my frequent trips to Oman and other Arab countries and other personal stuff," Hadi told reporters on Friday night, his first public appearance since Tuesday.

"They wanted to know about my relations with...other top Muslim clerics."

Police deny any involvement and Zanzibar police commissioner Mussa Ali Mussa said the Uamsho leadership "tricked people" with Hadi's disappearance.

"We think he was hiding somewhere in this town," he told Reuters on Saturday.

The Uamsho leaders charged in court by the police include Hadi, 41, and the group's chairman Sheikh Mselem Ali Mselem, 52.

Police said they will be detained until Thursday, when their bail conditions will be set.

(Additional reporting and writing by Drazen Jorgic and Fumbuka Ng'wanakilala, Editing by James Macharia and Michael Roddy)