Witnesses in northeastern Nigeria say a gunbattle between unknown assailants and police early Saturday had scores of residents in the town of Potiskum fleeing their homes for safety.

There are reports of gunfire around a police station and other sections of the town in Yobe State, with unconfirmed reports of casualties.

Potiskum is among 15 regions in northern Nigeria where President Goodluck Jonathan declared a state of emergency last week after days of deadly attacks.

Saturday's violent outburst follows two days of attacks when gunmen killed at least 20 people in northeastern Nigeria.

The attacks on Christians 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.

A purported spokesman for the radical Islamist sect Boko Haram claimed responsibility for the attacks. The spokesman, known as Abu Qaqa, also said Boko Haram was responsible for an attack on a church in Gombe state late Thursday that killed six people and wounded 10.

He said the attacks were in response to an ultimatum Boko Haram issued earlier this week, demanding that Christians in the largely Muslim north leave the region.

Boko Haram has claimed responsibility for a number of recent attacks in Nigeria, including a Christmas day bombing that killed more than 40 Christians.

President Jonathan has vowed to crush Boko Haram, but his critics complain that he has done little to rein in the group.