Fear and anger gripped Nigeria after a wave of Christmas Day bombings killed up to 40 people and wounded many more, sparking strong condemnation from Goodluck Jonathan, the Nigerian president, and the international community.
Hundreds of residents sought to flee the violence-torn city of Damaturu on Monday fearing further attacks and clashes between Islamists and the police, while about 30 Christian shops were burnt in the nearby city of Potiskum late on Sunday, the APF news agency reported.
The Nigerian Islamist group, Boko Haram, claimed responsibility for the wave of attacks on Sunday, which included bomb explosions at two churches and a suicide attack in the northeast.
Denouncing the attacks before a gathering in Abuja, Jonathan said: "There is no reason for these kind of dastardly acts.
Abba Moro, Nigeria's interior minister, told Al Jazeera's Ahmed Idris that the government planned to change its tactics in dealing with Boko Haram.
"He said they are going to re-strategise to deal with the situation... He said all options are open and government is assuring Nigerians that they are going to do everything possible to bring this cycle of violence under control as soon as possible," Idris reported the minister as saying.
Security stepped up
Our correspondent said security had been stepped up in the capital and in many other places, but Nigerians still had doubts about the ability of the government to deal with the situation.
"[Many Nigerians] feel that the security agencies are not up to the task. A lot of people are calling for a review of the security strategy and the security apparatus of government in the country. The government promised to do its best to handle the situation but so far this is not reassuring Nigerians that everything is under control," he said.
Speaking at his post-Christmas blessing on Monday in Vatican City, Pope Benedict XVI said only respect and reconciliation could bring peace, not violence.
He said he had learned with "profound sadness" of the "absurd" attack on the St Theresa Catholic Church.
"In this moment, I want to repeat once again with force: violence is a path that leads only to pain, destruction and death. Respect, reconciliation and love are the only path to peace," he said.
Catherine Ashton, the EU foreign policy chief, used strong words to condemn the attacks.
"I am profoundly shocked and saddened by the terrorist attacks which took place in several regions of Nigeria, including cowardly attacks on religious symbols and churches during the Christmas period, with appalling loss of human lives," she said in a statement.
"I condemn in the strongest possible terms these attacks and all other acts of terrorism," she said, voicing her solidarity and condolences to the victims and their families.
For its part, the White House condemned the "senseless" attack, offered its condolences to the Nigerian people, and pledged to assist authorities in bringing those responsible to justice.
In a statement, William Hague, Britain's foreign secretary, said: "These are cowardly attacks on families gathered in peace and prayer to celebrate a day which symbolises harmony and goodwill towards others."
Ban Ki-moon, the UN secretary-general, called in a statement for an end to religious violence in Nigeria.
Abu Qaqa, a spokesperson for Boko Haram, which advocates the enforcement of strict Islamic law in Nigeria, claimed responsibility for the bombings in a statement to the journalists' association of Maiduguri, capital of the group's heartland.
Al Jazeera's Idris, reporting from the scene of the first attack in Madalla, a satellite town of Nigeria's capital Abuja, said the assailant triggered an explosion after failing to gain access to the church on Sunday morning.
A government official said a second explosion also struck near a church, this time targeting a congregation in the central Nigerian city of Jos, killing a policeman. Another explosion was reported to have taken place at a church in the northeastern town of Gadaka, in Yobe state.
Police said a fourth explosion was triggered by a suicide bomber at the state security service building in Damaturu, also in Yobe. That blast killed four security officials and the bomber, they said.
Another explosion was also reported to have taken place in Damaturu on Sunday, but no further details were available.
Sunday's attacks occurred after days of battles between Boko Haram and security forces left more than 60 people dead near Maiduguri and Damaturu.
Boko Haram, whose name means "Western education is sacrilege" in the local Hausa language, is responsible for at least 504 killings this year alone, according to an Associated Press count.