The bombing attacks were carried out June 17 against churches in Nigeria's northwestern Kaduna state.
On June 18, Boko Haram, a militant Islamic sect that operates mainly in northern Nigeria and the country's capital of Abuja, claimed responsibility for the attacks.
"Thirty of those people were killed in the initial attacks at the churches in Kaduna, in the north of the country, and the subsequent retaliation by Christian youths," Nesirky noted. "The rest were reportedly killed in clashes between security forces and Muslims."
According to the spokesman, the UN high commissioner for human rights, Navi Pillay, has condemned the attacks by Boko Haram against places of worship and religious freedom.
"She said that these were blatant attempts to stir sectarian tensions and violence between two communities that have lived together peacefully for so long," said Nesirky. "Systematic attacks against a civilian population, on grounds such as religion or ethnicity, would amount to crimes against humanity. "