Witnesses say gunmen have killed at least 17 people in northeastern Nigeria, the latest in a series of deadly attacks in the region.

The attacks Friday happened in the Mubi district of Adamawa state, near the border with Cameroon. A local journalist told VOA that unidentified gunmen opened fire at three locations in the district.

Reports from the area say the attacks targeted people of the Igbo ethnic group.

Late Thursday, gunmen attacked a church during a prayer service in neighboring Gombe state, killing six worshippers and wounding 10. Police confirmed the attack and said an investigation was ongoing.

No one has claimed responsibility for that attack but suspicion fell on the Islamist militant group Boko Haram. Earlier this week, the group warned Christians in the largely Muslim north to leave the region in three days or face death.

Boko Haram has claimed responsibility for a number of recent attacks, including the Christmas day bombing of a Catholic church near Abuja that killed more than 30 people.

The sect, whose name means “Western education is a sin” in the Hausa language, has been blamed for dozens of deadly shootings and bombings mostly in the country's north.

It is fighting to implement a radical interpretation of Islamic law across Nigeria, which is divided between a primarily Muslim north and a mainly Christian south.

Nigerian President Goodluck Jonathan declared a state of emergency in 15 regions last week, closing parts of the borders with Niger, Chad, and Cameroon. Mr. Jonathan has vowed to crush Boko Haram, but his critics complain that he has done little to rein in the group.