At least 43 people were killed in the Democratic Republic of Congo after a Catholic church was attacked on Sunday. Officials initially reported that Islamist Allied Democratic Forces (ADF) rebels had carried out the attack in which terrorists raided the church located in the northeastern town of Komanda as worshippers gathered for prayer. Later on Monday, the self-named "Islamic State" group (IS) announced on the messaging app Telegram that it had been behind the deadly incident. What do we know about the attack on the Catholic church? Nine children were among those killed, according to MONUSCO, the UN peacekeeping mission in the country. According to reports, houses and shops surrounding the church were also set ablaze by the rebels. "These targeted attacks on defenseless civilians, especially in places of worship, are not only revolting but also contrary to all norms of human rights and international humanitarian law," the mission's deputy chief, Vivian van de Perre, said in a statement. DR Congo conflict: Who are the main players? 01:38 Congo military denounces attack Sunday's attack marked the end of a months-long period of calm in the region of Ituri, bordering Uganda. In February, 23 people had died in an attack by the ADF in the province's Mambasa territory. The Congolese military condemned what it described as a "large-scale massacre" on Sunday. It said the ADF had decided to take "revenge on defenseless peaceful populations to spread terror." Eastern Congo is considered one of the world's most dangerous regions. Nearly 130 different armed groups are said to be active across the country, many of which are focused on controlling the region's vast and valuable reserves of natural resources like coltan, cobalt, gold and diamonds. Hostilities earlier this year between Congolese forces and the M23 rebel group ended in a truce on July 19. Who are the ADF? The ADF is a long-standing insurgent group originating in Uganda and operating in eastern Congo. They have been responsible for the killings of thousands of civilians. The group often uses hatchets and machetes to carry out attacks. In 2019, the ADF pledged allegiance to the "Islamic State" group.