The first blasts went off within minutes of each other in the city of Zaria on Sunday. A third bomb was detonated at a church in Kaduna shortly after.
Reports put the number of injured at around 100 people.
According to the Press Association, militant Islamist group Boko Haram has claimed responsibility for the attacks.
Reuters reports that the latest church bombings sparked retaliatory attacks by Christian youths who pulled Muslims from their cars and killed them.
Boko Haram militants have killed dozens of Christians in attacks on churches in recent weeks. In the first weekend of June, at least 10 people were killed and more than 30 injured in a suicide bomb attack on a church in Bauchi.
The following weekend, at least seven people were killed in attacks on churches in Jos and Biu.
The attacks are being carried out in the largely Muslim north of Nigeria, where Boko Haram wants to enforce Sharia law.
The group declared this month that Christians were its “enemies” and that it would continue to attack churches “until we achieve our goal of establishing an Islamic state in place of the secular state”.