Dozens of people were killed on Sunday in an attack on a church in eastern Congo by a rebel group linked to the Islamic State.

The rebels, armed with guns and machetes, attacked the church in the city of Komanda around 1 a.m. while more than 100 people were holding a nighttime prayer vigil, according to local residents. More bodies were found in burned houses nearby.

The U.N. peacekeeping mission in the country, citing official reports, said that 43 people had died, including nine children. The Congolese Army said about 40 had been killed.

Children, mostly between the ages of 12 and 14, were taken hostage, according to the priest at the church, Sainte Anuarite. The parish was holding a celebration for its 25th anniversary when it was attacked.

Missionaries from Italy serve in the church, and the country’s deputy prime minister condemned the assault, saying that places of worship must be protected.

In a letter shared with The New York Times, the church had in June requested security from the local authorities ahead of the events. “Unfortunately, no intervention took place during the attack,” said Father Aimé Lokana Dhego, the priest at the church. He said the army and U.N. forces arrived only afterward “to count and assess the dead and damages.”