UN's mission to DR Congo said the explosion was caused by a home-made bomb set up for an ambush.
A makeshift bomb exploded inside a Catholic church in the city of Beni in the Democratic Republic of Congo's conflict-plagued east, injuring two people just an hour before a children's Confirmation ceremony was due to be held.
The head of police in Beni's town hall Narcisse Muteba Kashale said that the explosion occurred at 0400 GMT (6:00 am local time) on Sunday and that experts from the UN's mission to DR Congo had told "us it is a home-made bomb, a bomb that was set up for an ambush".
Beni's vicar general Laurent Sondirya said two people were injured in the blast, which went off before crowds would have gathered to attend the Confirmation ceremony.
"They were targeting a large crowd because the ceremony would bring together children, their parents and the faithful," he said, adding that "mass would not be postponed".
Traces of blood could seen at the entrance to the church in the aftermath of the explosion, an AFP reporter said, while shards of glass where scattered inside and the sound equipment was destroyed.
It marks the first time a building belonging to the Catholic Church, the city's largest religion, has been directly targeted in Beni territory, where the Allied Democratic Forces (ADF) militia is accused of killing 6,000 people since 2013, according to the Catholic episcopate.
Two imams in Beni known for speaking out against the ADF violence were shot dead in May, one inside the city's mosque and the other after evening prayers.
The ADF is the deadliest of an estimated 120 armed militia groups that roam the mineral-rich east of the vast central African country, many of them a legacy of two regional wars from 1996 to 2003.
The ADF is accused of killing hundreds of civilians since launching operations from a base in the jungle around Beni in November 2019.
In March, the United States said the ADF was linked to the Daesh group.