Nigerian President Goodluck Jonathan has said that spiralling violence blamed on the radical Islamist group Boko Haram is "even worse" than the country's 1960s civil war.
"The situation we have in our hands is even worse than the civil war that we fought," Jonathan said at a church service on Sunday, referring to Nigeria's 1967-70 civil war that killed more than a million people..
The death toll linked to violence blamed on the Islamist group has not reached anywhere near that level, but Jonathan cited the unpredictability and pervasiveness of the threat.
"During the civil war, we knew and we could even predict where the enemy was coming from ... But the challenge we have today is more complicated."
He said there are Boko Haram sympathisers in government.
"Some of them are in the executive arm of government, some of them are in the parliamentary/legislative arm of government, while some of them are even in the judiciary," Jonathan told a church service for armed forces remembrance day.
"Some are also in the armed forces, the police and other security agencies."
The president's remarks come on a day Ayo Oritsejafor, head of the Christian Association of Nigeria, told his followers that they should do what they have to in order to defend themselves from "ethnic and religious cleansing" at the hands of the radical Islamist group.
"We have the legitimate right to defend ourselves. We're also saying today that we will do whatever it takes. We are working things out between ourselves," Oritsejafor said.
Nigeria's government put into effect a 24-hour curfew on Saturday in the northeastern Adamawa state. Residents were ordered to stay indoors, and military personnel were deployed on the streets to enforce the curfew.
Last week the government declared a state of emergency in four of the areas worst hit by the violence, including Maiduguri and Damaturu.
Nigerian authorities said gunmen attacked a military vehicle in Maiduguri on Sunday afternoon.
Military spokesman Lieutenant Colonel Hassan Ifijeh Mohammed said the attack killed three civilians and wounded six civilians and one soldier, the Associated Press reported.
Local police commissioner Simeon Midenda said another attack on a tea shop on Saturday night in Biu, also in Borno state, killed three people, AP reported.
Earlier on Sunday, Christians on their way to religious services faced extra precautionary measures. "Churches have become very security conscious," said Al Jazeera's Haru Mutasa, reporting from the capital Abuja.
Worshippers were physically searched for weapons and explosives upon entering the places of worship.
| The history of radical Islamist group Boko Haram
"People are leaving [some areas]. We have been told that some families are heading to military barracks and police stations, Mutasa said on Saturday.
"There is a sense that people are scared in northern Nigeria, especially if they are non-Muslims."
Al Jazeera's Ahmed Idris, also in Abuja, said: "In Damaturu, it is virtually almost an empty part of town because people have really left those areas affected by the violence.
"In Potiskum it's the same situation."
The government meanwhile said it had engaged alleged Boko Haram fighters in Potiskum, a northeastern town in Yobe state, in clashes that continued through Friday night.
Boko Haram has claimed responsibility for at least two of the four separate attacks over the last few days.
The group, whose name loosely translates to "Western education is forbidden", is believed to favour implementation of Islamic law across Nigeria, a multi-ethnic nation of more than 160 million people.
Last Sunday, a spokesman for the group issued an ultimatum for Christians living in Nigeria's mainly Muslim north to leave the region or they would be killed.
The ultimatum came after President Goodluck Jonathan declared a state of emergency in parts of four states hit hard by violence blamed on Boko Haram, particulary Christmas bombings that killed at least 40 people.
Attacks on Friday left tens of people dead, eight of them killed after gunmen opened fire on worshippers in a church in Yola, a hospital source said.
Earlier on Friday, at a town hall in Mubi, also in Adamawa state, at least another 12 people were killed after armed men opened fire on a group of people from the Christian Igbo community who were gathered there.
Idris said that residents told him the incident occurred at a meeting to discuss the deaths of four others from the Igbo community who were killed in an attack in the town on Thursday.
Boko Haram claimed responsibility for Friday's attack in Mubi, local media reported.
The group, via a purported spokesman who goes by the name Abul Qaqa, also claimed responsibility for a separate church shooting attack in the town of Gombe on Thursday night, which left nine people dead.