Local residents said sporadic gunfire, which began around 1700 GMT on Monday, could still be heard in Damaturu on Tuesday but the authorities did not say where the clashes were taking place or whether there were any casualties.

"In view of the prevailing security situation in the State Capital, Governor Ibrahim Gaidam has approved the immediate imposition of a 24-hour curfew within Damaturu metropolis," a government statement said on Tuesday.

"Residents are hereby directed to remain in their homes while officers and men of the Joint Task force and other security agencies continue with their effort to ensure peace and security and the protection of life and property."

In November, 65 people were killed in coordinated attacks claimed by Islamist sect Boko Haram on churches, mosques and police stations in Damaturu.

The group is waging an insurgency against President Goodluck Jonathan's government, and clashes between it and the military have become an almost daily occurrence in northeast Nigeria.

It was not clear if the violence in Damaturu was related to religious killings in other parts of northern Nigeria on Sunday.

At least 52 people were killed on Sunday in religious rioting in north central Kaduna sparked by three suicide bombings against churches that killed 16.

Boko Haram has claimed deadly attacks on churches in the past.

The violence has stoked fears of a wider sectarian conflict in Nigeria, an OPEC member and Africa's top oil producer that is home to the world's largest equal mix of Christians and Muslims.

The Islamists' leader, Abubakar Shekau, has said the attacks on Christians were in revenge for the killings of Muslims.