Islamist Boko Haram is accused of killing 25 people, including three soldiers, in attacks in the Madagali and Hong areas of Adamawa state on the border with Cameroon.
The attackers arrived on motorcycles and shot at people at a market on Tuesday evening, according to the authorities.
"We are still looking for more bodies," an official said.
In addition, at least five people were killed when a mosque in the northwestern state of Kebbi was attacked on Wednesday, the state news agency NAN reports.
Attacks carried out by jihadists and criminal gangs are common in Nigeria, especially in the north.
