Nigeria's Boko Haram has threatened to carry out more attacks, a day after a series of blasts and gun battles claimed by the group killed more than 100 people in the country's northeast, the Nigerian Red Cross has said.
Ibrahim Bulama, an official from the humanitarian organisation, said on Sunday that the death toll is expected to rise as local clinics and hospitals tabulate the casualty figures from Friday's attacks in Damaturu, the capital of rural Yobe state.
A spokesman for the Islamist armed group, using the name Abul-Qaqa, promised "more attacks are on the way", speaking hours after witnesses reported "scenes of carnage".
The US embassy in Nigeria has issued an emergency warning to its citizens living there that bomb attacks could be possible at luxury hotels in the capital Abuja.
Boko Haram, which means "Western education is sacrilege", has claimed responsibility for previous attacks and the latest was the deadliest since the group attacked a UN building in Abuja in August, killing at least 20 people.
"We will continue attacking federal government formations until security forces stop their excesses on our members and vulnerable civilians," Abul-Qaqa said in an interview with the the Daily Trust, the newspaper of record across Nigeria's Muslim north.
Suleimon Lawal, the police commissioner of Damaturu, told Al Jazeera a suicide bomber drove a vehicle apparently laden with explosives into a building housing the anti-terrorist court.
Lawal said the attack killed 53 people but he did not disclose how many among the casualties were security officials.
"I know for a fact that there're Nigerian groups in and outside the government, including the media, who are suggesting that the government should try to talk to Boko Haram, but my own impression is that they don't seem to be particularly ready or inclined to talk."
- Nii Akuetteh, former executive director of Africa Action in Washington, DC
"The explosives rocked the building and there were casualties. Two of them [suicide bombers] perished in the bomb," he said.
Lawal insisted the group was not gaining an upper hand and vowed that it would be crushed.
"My strategy is a security strategy [that] I cannot disclose on air. So as they're not [Boko Haram] disclosing their security strategy, I don't think it is safe for me to tell the whole world what I am doing," he said.
The violence followed a series of attacks reported in the neighbouring cities of Maiduguri and Potiskum on Friday afternoon.
"There's that fear that something might possibly happen again," Ibrahim Bulama, a spokesman for the Nigerian Red Cross, said.
Security vehicles torched
News agencies, quoting officials, said after the attack on the building, armed men went through Damaturu, blowing up a bank and attacking at least three police stations and five churches, leaving behind their rubble.
People began hesitantly leaving their homes on Saturday morning, after seeing the destruction left behind, which included military and police vehicles burned by the armed men, with the burned corpses of the drivers who died still in their seats.
Boko Haram wants the strict implementation of Islamic law across the nation of more than 160 million people, which has a predominantly Christian south and a Muslim north.
Nii Akuetteh, a former executive director of Africa Action, a Washington-based rights group, said the group appeared to be growing strong.
"The government has been saying that it will deal with them and that it will get a handle on the problem, but it's not been able to," he told Al Jazeera.
"Previously, the attempt made was to try and fight them militarily - to send the secuirty forces after them - but that has created its own problem.
"I know for a fact that there're Nigerian groups in and outside the government, including the media, who are suggesting that the government should try to talk to Boko Haram.
"But my own impression is that they don't seem to be particularly ready or inclined to talk."
Split into factions
The AP news agency, quoting a diplomat, said the government was facing an increasingly dangerous threat from Boko Haram, adding that the group had split into three factions, one allied with al-Qaeda's North Africa branch.
It said one faction remains moderate and welcomes an end to the violence while another wants a peace agreement with rewards similar to those offered to MEND, which has been fighting for a greater share of Nigeria's oil wealth.
The attacks occured just before Eid al-Adha, or the feast of sacrifice, celebrated by Muslims around the world.
Police elsewhere in Nigeria had warned of violence in the run-up to the celebration in the country that has previously been rocked by religious violence.
Goodluck Jonathan, Nigeria's Christian president who took office amid religious and political rioting that saw at least 800 die in April, cancelled a trip to his home state of Bayelsa for his younger brother's wedding on Saturday.
His spokesman, Reuben Abati, said the president did not consider those who launched the attacks "true Muslims," as the assault came during a holy period.
Abati also promised that "every step will be taken" to arrest those responsible - the same pledge made again and again as Jonathan has visited other sites bombed by Boko Haram.
"The security agencies will tell you that what happens on this scale is even a fraction of what could have happened considering the scope of the threat," Abati said.
"The security agencies are busy at work trying to make sure the will of the majority of the Nigerian people is not subverted by a minority [group] with a suicidal streak."
Speaking to Al Jazeera, Isaac Olawale, a researcher for the Oxford University Centre for Research on Inequality, Human Security and Ethnicity, said: "The present attempt to deal with the problem using confrontational strategies will not work.
"There is poverty all over the country and an increased number of Nigerians are jumping into the warm embrace of ethnic, chauvinist and religious fundamentalism.
“Boko Haram expresses some of the social upheavals we are witnessing in Nigeria.”