The attack happened in Kaduna, scene of many sectarian attacks.
The blast was caused by at least one vehicle being driven towards the church loaded with explosives, witnesses said.
No group has said it carried out the bombing, but Islamist group Boko Haram has been involved in several similar attacks in the area.
The attack happened at St Rita’s church in the Malali neighbourhood of the city.
National Emergency Management Agency spokesman Yushua Shuaib told AP news agency initial reports suggested the attack was by a suicide bomber.