KADUNA, Nigeria (AP) — Aid workers searched for bodies yesterday among charred vehicles and destroyed market stalls after a trio of church bombings sparked reprisal killings in northern Nigeria, officials said. The Nigerian Red Cross said the death toll had more than doubled, to 50 people.

The radical Islamist sect known as Boko Haram yesterday claimed responsibility for Sunday’s suicide attacks at two churches in the city of Zaria and another in the city of Kaduna that left 21 people dead, according to an initial count.

The reprisals highlight festering religious tensions in Nigeria, a nation of more than 160 million people. The attacks occurred in the religious flashpoint state of Kaduna that sits at the border between the country’s predominantly Muslim north and its mainly Christian south. A history of attacks and counter-attacks between the two communities means that authorities are often cautious about releasing death figures.

Officials initially said 21 people were killed in Sunday morning’s blasts. But the Nigerian Red Cross said late Sunday that the death toll had jumped to 50, to include reprisal killings. Officials refused to give a breakdown clarifying who died in the initial blasts and who was killed in reprisals.

“We did that for a reason,” said Andronicus Adeyemo, deputy head of disaster management at the Nigerian Red Cross. “Those figures are sensitive.”

Authorities fear that a breakdown of the deaths will trigger revenge killings. Most of the victims killed in church on Sunday are presumed to be Christian and most of those killed in reprisal attacks are presumed to be Muslim, raising concerns that a distinction between initial and reprisal deaths will be interpreted as a Christian and Muslim breakdown.

At about 5:00 pm Monday, men armed with bombs and guns launched attacks in Damaturu, the capital of Yobe state about 450 miles (720 kilometres) north of Kaduna, said Yobe state police chief Patrick Egbuniwe. It was not immediately clear what parts of Damaturu were attacked, whether there were any casualties, or whether the violence could have been linked to the killings in Kaduna.

But Egbuniwe said, “Terrorists are trying to show that they can’t be stopped.”

Fatima Garba, a citizen who lives near government buildings, said she could still hear gunshots being fired at about 10:00 pm.

In November, Boko Haram claimed responsibility for bombings and shootings in and around Damaturu city — some at Christian churches — that left more than 100 people dead.

In Kaduna, relief officials said they were still collecting bodies yesterday. Most victims were petty traders and transporters such as bus drivers and motorcycle taxi drivers, who are presumed to be Muslim and who commute daily to the predominantly Christian southern part of the city. An Associated Press reporter saw charred motorcycles, buses and stalls that littered deserted streets in predominantly Christian neighbourhoods yesterday. The state government initially imposed a 24-hour curfew, but relaxed it yesterday to a dusk-until-dawn curfew.

“We are still picking up bodies from reprisals,” Musa Illalah, the National Emergency Management Agency co-ordinator for Kaduna State, said yesterday morning.

The group known as Boko Haram said in an e-mail that it was responsible for the attacks.

“Allah has given us victory in the attacks we launched (Sunday) against churches in Kaduna and Zaria towns which resulted in the deaths of many Christians and security personnel,” the statement said in the local Hausa language.

Boko Haram, which means “Western education is sacrilege” in Hausa, is waging an increasingly bloody fight with Nigeria’s security agencies and the public. More than 580 people have been killed in violence blamed on the sect this year alone, according to an AP count.

As news of the church attack filtered through the city Sunday morning, young Christians took to the streets in violent protest. An AP reporter saw billows of smoke over a mosque in a predominantly Christian part of the city. People had mounted illegal roadblocks and were seen harassing motorists. A motorcycle rider in that same neighbourhood lay seriously hurt and bleeding by the road side. Motorbike riders often become easy targets during reprisal attacks by Christians. Police said that about 1,000 Muslims took refuge at police quarters.

The first two suicide bomb attacks occurred Sunday within about 10 minutes of each other in different parts of the city of Zaria. Thirty minutes later, a third attack targeting a church rocked the nearby city of Kaduna. All three attacks wounded at least 100 people, an official who works with a relief agency involved in rescue efforts had said Sunday. He spoke on condition of anonymity because he wasn’t authorised to speak to journalists.

Churches have been increasingly targeted by violence in Nigeria. This is the third weekend in a row that Boko Haram is claiming responsibility for church attacks in central and northern Nigeria. Statements attributed to the group said they were responsible for church attacks in the first and second Sundays of June that killed at least 21 people.

That threat has prompted churches to boost their security.

Police said security guards stationed outside the three churches had kept the number of deaths relatively low.

“In most of the attacks, they (the attackers) did not reach their desired location,” national police spokesman Frank Mba told Nigeria’s state-run television.

The most deadly attacks seem to have targeted Christian holidays: An Easter Day blast in Kaduna left at least 38 people dead, and a Christmas Day suicide bombing of a Catholic church near Nigeria’s capital killed at least 44. Boko Haram claimed responsibility for both attacks.