Ethiopia’s military has killed more than 40 men suspected to be linked to the massacre of at least 100 people, including children, in the Benishangul-Gumuz region, state media report.
Five current and former government officials were also detained over the security crisis, the reports added.
The assailants torched the homes of sleeping villagers, and shot and stabbed people in Wednesday’s attack.
The attack came a day after Prime Minister Abiy Ahmed visited the region.
It is unclear who the attackers were, but they appeared to have targeted ethnic minority communities viewed as “settlers” in the region, rights group Amnesty International said.
Ethiopia has seen a surge in political, ethnic and religious violence in recent years.
It had the highest number of internally displaced people in Africa in 2018 – about 1.8 million.
Conflicts have been largely fuelled by groups demanding more land and power, with attempts to drive out people they regard as outsiders.
Mr Abiy described the massacre as tragic, and said the government had deployed a force to the area to help find a solution to the conflict.
State media did not give the identity of the 42 people killed in the military operation to hunt down the attackers.
It said weapons, including bows and arrows, had been seized, the reports said.
A deputy minister in the government was among the five people arrested, state media reported.
Some of the five were “supposedly involved in [the] security crisis” while others had been detained because they had “not fulfilled their responsibility appropriately”, the reports said.
What happened during the latest attack?
A spokesman for the state-linked Ethiopian Human Rights Commission told the BBC that gunmen carried out the attack in the western Benishangul-Gumuz region at around 04:00 local time (01:00) on Wednesday.
“They descended on a village and while their victims were asleep they set their homes on fire but also they shot and killed civilians,” Aaron Maasho said.
Amnesty International said it had spoken to five survivors and an official who reported that members of the ethnic Gumuz community attacked the homes of people from the Amhara, Oromo and Shinasha communities.
“While Amnesty international is unable to verify identities of the perpetrators, this attack appears to be the latest targeting of people of ethnic minorities in the area.
“With dozens still unaccounted for and homes still ablaze, the death toll is likely to rise and there must be an urgent investigation into this horrendous attack,” it added in a statement.
What is the bigger picture?
Ethiopia’s is Africa’s most populous state after Nigeria. It has a population of more than 100 million split into about 80 ethnic groups.
Mr Abiy became prime minister in 2018 after mass protests forced his predecessor to resign.
He promise to end authoritarian rule, and introduced sweeping reforms that led to the unbanning of political groups and the release of thousands of prisoners.
The end of state repression also to a surge in ethnic nationalism which spilled over into violence.
Ethnic and political groups which felt suppressed under the former regime demanded more autonomy for their regions, and greater recognition of their language and cultural rights.
Is the violence linked to the conflict in Tigray?
No, but the region’s now-ousted ruling party, the Tigray People’s Liberation Front (TPLF), saw Mr Abiy as a threat to the “ethnic federalism” that it had helped introduce in Ethiopia after it took power at the end of a guerrilla war in 1991.
It had created the Ethiopian People’s Revolutionary Democratic Front (EPRDF), a coalition of four ethnically-based parties, to rule at the centre.
Mr Abiy scrapped the coalition last year, replacing it with his new Prosperity Party (PP).
He supporters see the PP as helping to forge unity by bringing together ethnically-based parties from across Ethiopia.
But unlike the three other parties in the coalition, the TPLF refused to dissolve and merge with the PP.
This led to a permanent rupture in relations between the two sides, and the TPLF was not represented in the federal government for the first time since 1991.
The party retreated to its regional stronghold of Tigray, and held regional elections in September in defiance of a decision at federal level to postpone all elections because of the outbreak of coronavirus.
This marked a significant escalation in tensions, which eventually led to the outbreak of conflict in Tigray last month.
Hundreds, or even thousands, of people are thought to have been killed in that conflict, while about 50,000 have fled to neighbouring Sudan.