Authorities in Uganda said on Monday that 20 people had been arrested in connection to a gruesome attack on a school in Mpondwe, western Uganda, near the border with the Democratic Republic of Congo (DRC).

School's head teacher, director among those arrested

Some 42 people were killed when militants of the Allied Democratic Forces (ADF) rampaged the Lhubiriha Secondary School, burning, stabbing and even shooting the victims.

"Twenty arrests have been made of suspected collaborators, suspected ADF collaborators," police spokesman Fred Enanga told a press conference.

In a separate statement, it was revealed that among those arrested were the school's head teacher and its director.

The perpetrators fled back into the DRC, reportedly taking an unknown number of students hostage, with authorities saying that 15 people from the community, including five girls, were still unaccounted for after the attack.

"Their action -- the desperate, cowardly, terrorist action -- will not save them," President Yoweri Museveni said Sunday in his first statement on the attack, vowing to hunt the militants "into extinction."

Joe Walusimbi, the Resident District Commissioner of the area where the school was located, said most of the identified victims had been buried on Sunday, with more funerals taking place on Monday.

A 'barbaric' attack

Of the 42 victims, some 37 were students. The oldest among the victims so far identified was a 95-year-old woman and the youngest was a 12-year-old girl who had just begun secondary school studies.

The attackers are said to have shot, hacked with machete and burned the youngsters to death in their dormitories.

"An attack on innocent children is barbaric, is inhumane and of course constitutes crimes against humanity," Enanga said.

"As a country, we continue to stand by each other in the fight against terrorism. No matter how heinous the attack or how brutal or inhumane the methods used, the ADF will not be able to succeed in demolishing the solidarity of Ugandans in the fight against terrorism and extremism," he added.

The killings at the secondary school represent the deadliest attack in Uganda since Somalia-based al-Shabab carried out twin bombings in Kampala in 2010 that left 76 people dead.

The ADF is an "Islamic State"-affiliated armed group, which has been historically linked to predominantly Muslim Ugandan rebels opposed to President Museveni.

The ADF has been blamed for thousands of civilian deaths in the DRC since the 1990s, and in March 2021 it was officially listed as a terrorist organization by the United States.