At least 24 people were killed in coordinated suicide bombings against two churches in northern Nigeria, plus reprisal attacks in Kaduna, doctors said Sunday.
The twin suicide attacks struck the ECWA Goodnews Church and the King Catholic Church in the Christian area of Zaria, one of Nigeria's oldest cities, dpa reported.
Both churches were holding Fathers' Day celebrations, according to witnesses.
The double bombings sparked retaliation attacks by Christian youths in Kaduna, with sources saying gangs burnt a mosque in the city, killing several people, and attacking otheres with sticks and swords.
Some 125 injured in the attacks, the local Daily Trust newspaper reported.
A dusk-to-dawn curfew was imposed in the region in the wake of Sunday's events.
The militant Islamist Boko Haram sect has carried out waves of attacks against Christian churches and schools in recent months, although no group has yet claimed responsibilty for Sunday's attacks.
President Goodluck Jonathan, also at a church service marking the Father's Day Celebrations, condemned the attack, and pledged to bring perpetrators to justice.