Fresh explosions and gunfire rocked a northeastern Nigerian city on Monday, a day after suicide attacks claimed by Islamists and reprisal violence by rampaging Christian mobs left 52 people dead.
The two days of violence has underlined the precarious state of security in Nigeria's mainly Muslim north, where an insurgency by Islamist group Boko Haram that has left hundreds of people dead has been concentrated.
The new outbreak of unrest in the city of Damaturu, previously hit by heavy violence blamed on Boko Haram, came after authorities said they had restored calm in northern Kaduna state, where Sunday's attacks occurred.
Boko Haram claimed responsibility for three suicide attacks on churches in Kaduna state on Sunday which led to deadly rioting, while police blamed the group for the violence that broke out in Damaturu.
A military commander said the Damaturu unrest on Monday occurred after authorities arrested a Boko Haram suspect, prompting other members of the group to respond by setting off explosives and shooting indiscriminately.
It was not clear if there were any casualties. The commander said the situation had been brought under control, though residents said they continued to hear shootings and explosions.
"We arrested a Boko Haram suspect with bombs and so his comrades were not happy with the development," said Colonel Dahiru Abdussalam, commander for a military task force in Yobe state, where Damaturu is the capital.
"And therefore Boko Haram elements came out in a well coordinated manner and began shooting and setting off explosions in the city. But we have contained the situation."
Sunday's church bombings, an almost weekly occurrence in Nigeria in recent months, left at least 16 dead and triggered a wave of fierce revenge attacks that killed more than twice as many.
Officials on Sunday had imposed a state-wide 24 hour curfew in Kaduna state, as rescuers combed deserted streets for bodies.
The mobs had moved through the streets in the state capital Kaduna on Sunday with machetes and clubs while also torching at least three mosques, petrol stations and vehicles. A number of the victims' bodies were burnt.
Boko Haram, responsible for more than 1,000 deaths since July 2009, said the attacks at a church in Kaduna city and two churches in the nearby city of Zaria were a response to the "atrocities Christians perpetrated against Muslims."
"Allah has given us victory in the attacks we launched against churches in (the cities of) Kaduna and Zaria which resulted in the deaths of many Christians and security personnel," said the Boko Haram statement.
Police said the blasts killed at least 16 people, sparking young Christians carrying clubs and machetes to wreak havoc around Kaduna city.
"As of the last count we have 52 dead bodies picked up from the affected areas. We have more than 150 injured," said a senior rescue official who asked to not be named as he was not authorised to issue death tolls.
"Most of the victims were those killed in reprisal attacks."
The ban on movement has since been relaxed, Kaduna state police spokesman Aminu Lawan told AFP, with movement allowed between 2:00 pm and 6:00 pm.
Following presidential elections last year, rioting in Kaduna state left more than 500 people dead, mostly Muslims.
A resident of Kaduna city's Goni Gora area claimed he saw soldiers shoot dead three members of a Christian mob late on Sunday as they sought to destroy a mosque.
Police spokesman Lawan said he had received no reports of fighting between rioters and security forces.
While banks and shops were closed Monday as troops patrolled, the lockdown did not apply to doctors and nurses, state government spokesman Saidu Adamu said.
"Many of (the injured) need surgery, but a shortage of blood is stalling treatment," a Red Cross official in Kaduna said.
The first blast struck ECWA Goodnews Church in Zaria city early Sunday. The second explosion went off 10 minutes later at the Christ the King Catholic church in Zaria, a police statement said.
The third blast hit the Shalom Church in Kaduna city moments later.
As their insurgency has intensified, Boko Haram's demands have varied widely, prompting speculation that the group is composed of disparate cells, including a hardcore Islamist wing.
The extremists have previously said they intended to create an Islamic state across the mainly Muslim north of Nigeria, Africa's most populous nation of 160 million, where the south is majority Christian.