A number of villages in Borno State have been attacked by suspected Boko Haram militants.
One account, from Reuters news agency, said suspected Islamists killed at least 10 people in one attack.
The reports spoke of churches being attacked with bombs and guns.
The incidents are said to have taken place near Chibok, the Borno state town where some 200 schoolgirls were abducted in April.
A state of emergency is in force in northern Nigeria because of an increasingly violent campaign by Boko Haram.
In one of the incidents, the militants apparently opened fire during an early morning church service in a village called Kwadakau, killing several people.
Local residents appealed for help. BBC