Nigerian police suspect a radical Muslim group is behind the shooting death of a rival cleric in northeastern Borno state.

Authorities believe Boko Haram members killed Sheik Ibrahim Birkuti outside his home in the town of Biu.

The gunmen were riding motorcycles when they opened fire on the cleric.

Birkuti had been critical of Boko Haram's use of violence in the volatile region.

Officials say that in recent months Boko Haram members have targeted and killed police, political leaders, and religious leaders, mostly in Borno state.

The group is fighting to establish Islamic law across Nigeria. Its name means “western education is sinful.”