A homemade bomb was thrown into a madrasa in Delta State in southern Nigeria, the police said, wounding seven people and escalating tensions between Muslims and Christians after several church bombings across the nation. Six of the wounded were children younger than 9. They were learning the Koran at the Islamic seminary, or madrasa. The attack on Tuesday night followed the Christmas Day bombings of churches and other targets by the Islamist militant group Boko Haram that killed 32 people and seemed aimed at igniting sectarian strife.

At a meeting with President Goodluck Jonathan on Wednesday, Ayo Oritsejafor, head of the Christian Association of Nigeria, an umbrella group, said that Christians had become victims of “Islamic Jihad.”