Yobestate police commissioner Sanusi Rufai said it was nevertheless too early to know who was behind the attack, which happened either late on Saturday or before dawn on Sunday.
In July and August 2012 suicide bombers tried but failed to kill the shehu - or traditional ruler - of the Borno emirate in north-east Nigeria as well as the emir of Fika in Yobestate.
Last week, President Goodluck Jonathan declared a state of emergency in three north-eastern states - Borno, Adamawa, and Yobe - after a series of deadly attacks by militant groups.