The number of casualties in the blasts in the neighbouring cities of Zaria and Kaduna was not immediately clear. Police and the military cordoned off the areas around the churches.
The state-run National Emergency Management Agency (NEMA) said the blasts happened in the Wusasa and Sabongari districts of Zaria, previously targeted by the Islamist group Boko Haram.
Residents in the areas said many people were injured in the attacks on the Christ the King Catholic Cathedral and ECWA GoodNews Church.
"Many people in the church were injured but I have not seen any dead bodies," a woman who was in the church in Wusasa at the time of the explosion said by telephone from her hospital bed.
Several residents in Sabongari said the church was badly damaged.
"I went close to the church but could not access it due to heavy police and military security deployed around it," resident Mahmud Hamza told AFP.
"From where I stood I could see a badly destroyed church still burning from the explosion. It is obvious there were deaths from the scale of the damage and the fire," he added.
Another resident spoke of seeing bodies being taken out of the church.
Officials later reported a third bomb attack on a church in Kaduna, but there were no immediate reports of casualties.
Boko Haram has claimed responsibility for a series of attacks targeting churches in Africa's most populous nation and largest oil producer.