CAIRO (NYTIMES) - Dozens of people were killed in Ethiopia over the weekend, when three villages were assaulted by an armed rebel group, the government and human rights organisations said Monday (Nov 2), the latest in a spate of attacks that threaten the stability of Africa's second-most populous nation.

The assailants late Sunday killed at least 54 people from the ethnic Amhara group in the Oromia region, Amnesty International said.

The attackers, who authorities said were from the Oromo Liberation Army, a group that broke off from a once-banned political party, attacked three villages in the West Welega Zone. They killed the victims after luring them to a school compound, then plundered what they could from the three villages and set everything else on fire.

The Ethiopian Human Rights Commission, an independent national rights group, said in a statement posted on Twitter that there were up to 60 assailants. The commission, which put the death toll at 32 but said the final number was likely to be higher, said the attack came a day after federal forces had pulled out from the area even though it was susceptible to attacks.

Sunday's attack underscored how relations between Ethiopia's ethnic groups are fraying even as Prime Minister Abiy Ahmed tries to unite the country's ethnically federated states.

As the country has opened up in recent years, ethnic grievances around resources, land, internal borders and political power have intensified. This is particularly true among the Oromo and Amhara, who together make up more than 60 per cent of the country's population of more than 108 million people.

Abiy, a Nobel Peace Prize laureate, on Monday condemned the attacks, saying "Ethiopia's enemies" were determined to either "rule or ruin the country."

"The strategy they are using is to arm civilians and carry out barbaric attacks based on identity," he said in a statement posted on Facebook.

"It is heartbreaking to see this happen as a citizen and as a leader."

Simmering ethnic tensions and violence have dogged Abiy's administration the past two years.

Since he came to power in 2018, he has introduced a number of reforms, including freeing political prisoners, legalising previously banned opposition groups, and making peace with neighbouring Eritrea, a longtime foe.

But the reforms and the country's new openness have also unleashed a host of problems, parties and personalities that have directly challenged Abiy's rule.

These include the Oromo Liberation Army, an armed splinter wing of the political party the Oromo Liberation Front, which Abiy welcomed back from exile.

The group has not taken responsibility or commented on the latest attacks.

But authorities have in the past accused them of undertaking actions with the aim of inciting ethnic tension and toppling the government. This included their alleged involvement in the killing of Hachalu Hundessa, a prominent Oromo singer who was gunned down in the capital of Addis Ababa in late June.

Hundessa's death incited widespread unrest and violence, with hundreds killed, thousands arrested and the government clamping down on media outlets and journalists.

In the Oromia region, members of religious and ethnic minorities like the Amhara were reportedly attacked, resulting in deaths, displacement and widespread property destruction.

The latest bout of violence reflects how political polarisation in Ethiopia generally occurs along ethnic lines, particularly as tension has built over the government's decision to postpone this year's general elections.

Even as Abiy battles a confluence of crises, including the coronavirus pandemic, record floods and displacement besides swarms of desert locusts that are ravaging crops, opposition to his rule has been intensifying on the ground.

In September, Ethiopia's northernmost region of Tigray held parliamentary elections despite Abiy calling them "illegal" and "unconstitutional." On Monday, rights groups urged the government to investigate why the government troops had abruptly left the area before the attacks.

It "raises questions that must be answered," Deprose Muchena, Amnesty International's regional director for east and southern Africa, said in a statement.

On Monday, Abiy said security forces had been deployed into the area.

"This will not drag us backward," Abiy said. "It won't shift us from our goal. It will not make us lose hope and stop." Abdi Latif Dahir.