Fresh sectarian violence has flared in two northern Nigerian cities, after church bombings and rioting killed at least 50 people on Sunday.

Police told VOA Tuesday that at least three security officers were killed after gunfire erupted in the city of Damaturu. Some residents blamed the Islamist militant group Boko Haram, which has claimed responsibility for many attacks in northern Nigeria.

Meanwhile, officials in Kaduna say protesters took to the streets Tuesday, setting buildings on fire and burning tires. The Kaduna state commissioner of information, Saidu Adamu, told VOA that authorities are blaming both Christians and Muslims for the unrest in the religiously mixed city.

“We can not pinpoint one particular religion to say they are responsible now. Every group is responsible. We are not trying to pinpoint. All we are trying to do now is to make sure the crisis is brought to an end.”

The unrest has prompted officials in both Damaturu and Kaduna to impose 24-hour curfews.

Violence in the north has escalated in recent weeks. Boko Haram claimed responsibility for Sunday's attacks on three churches as well as church attacks the previous two weeks.

The violence has continued despite increased security by Nigeria's anti-terrorist Joint Task Force.

Nigeria has a history of sectarian violence, especially in the country's Middle Belt, where the mainly Muslim north meets the predominantly Christian south.

Boko Haram says it is fighting for an Islamic state and does not recognize the Nigerian government or the constitution.