At least 40 people died in Sunday's attack in Owo in Nigeria's Ondo state, area governor Oluwarotimi Akeredolu now says.
Previously the authorities had said 22 people died.
In a statement, the governor said that 61 people were currently admitted in nearby hospitals for treatment and 26 had been discharged.
There were 127 people in the church when the attack happened, he said.
He added that the government would set up a memorial park to remember the attack victims.