Gunmen have killed 32 people and torched more than 20 houses in a raid in western Ethiopia, a regional administrator said on Monday.

The killings were carried out on Sunday by an armed group called OLF Shane in the Western Wollega Zone of the Oromiya region, administrator Elias Umeta told Reuters.

"We buried today 32 of them. About 700 to 750 people were also displaced from the area," he said.

OLF Shane split from the Oromo Liberation Front (OLF), an opposition party that spent years in exile but was allowed to return to Ethiopia after Prime Minister Abiy Ahmed took office in 2018. Sporadic violence has rocked Ethiopia since then.

Ahmed won the Nobel Peace Prize in 2019 "for his efforts to achieve peace and international cooperation, and in particular for his decisive initiative to resolve the border conflict with neighboring Eritrea."

OLF Shane says it is fighting for the right of the Oromos, the largest ethnic group in Ethiopia. But there was no immediate known motive for the killings, Elias said.

"They were executed after they were told by the armed group they want to have a meeting with them," he said.

The state-run Ethiopian Human Rights Commission said the attack had targeted people from the ethnic Amharic group.

"They were dragged from their homes and taken to a school, where they were killed," Daniel Bekele, the commission's chief commissioner, said in a statement, adding the death toll could be higher.

"These gruesome killings of civilians are unconscionable and flout basic principles of humanity."

The latest killings add to recent incidences of violence in various parts of Ethiopia.

Last week clashes between two Ethiopian states Somali and Afar that have long disputed their border killed at least 27 people.

In mid October, at least 12 people were killed in the Metakal zone of Benishangul-Gumuz region. That followed two attacks in the same zone in September, when 45 people were killed.