Dozens more were missing following the attacks, local officials told PM News in Lagos and the Nigeria Sunday Tribune.
Fourteen nomadic herders were killed by gunmen who opened fire in a village in Borno state, local government representative Alhaji Garba Ali said.
About two dozen members of a vigilante organization died in an ambush in a Borno forest at Monguno, located about 105 miles from the state capital of Maiduguri. Local officials who asked not to be named told PM News and the Tribune the attackers were wearing military uniforms and the group of more than 100 young vigilantes, who were searching for Boko Haram members, followed them into the woods, believing they were government troops.
"They took them to the middle of the forest before descending on them," PM News quoted an official as saying.
The Tribune said about three dozen members of the vigilante group were missing.
More than 3,600 deaths have been attributed to the Boko Haram insurgency since 2009. The violence led Nigerian President Goodluck Jonathan to declare a state of emergency in the northeast region of the country in May.
Boko Haram seeks the creation of an Islamic state in Nigeria.