A series of church bombings has sparked reprisal killings in northern Nigeria taking the death toll to at least 50 people.
A radical Islamist sect claimed responsibility for Sunday's suicide attacks at two churches in the city of Zaria and another in 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.
Officials initially said 21 people were killed in Sunday morning's blasts. But the Nigerian Red Cross said later 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.
In Kaduna, relief officials said they were still collecting bodies on Monday. 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.
The group known as Boko Haram said 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," it said.
Boko Haram, whose name means "Western education is sacrilege" is waging an increasingly bloody fight with Nigeria's security agencies and public. More than 580 people have been killed in violence blamed on the sect this year alone.