An aerial strike on the grounds of a church in Ethiopia's Oromiya region killed eight people and injured five as they collected corn, two witnesses and an opposition political party said.

Government spokesperson Legesse Tulu dismissed the accounts of the air strike as "an absolute lie".

Peace talks between Ethiopia's government and the rebel Oromo Liberation Army (OLA) aimed at ending a decades-old conflict ended without a deal in November, leading to sporadic attacks in Oromiya, the country's largest region. 

The compound of the Baro Full Gospel Church in the Horo Gudru Wellega zone, around 200 km northwest of the capital Addis Ababa, was attacked on Monday morning, when people were gathering to collect corn from a field, witnesses said.

Two deacons, two keyboard players from the church band, and a singer in the choir were among the dead, said a member of the church who requested anonymity.

"I heard a strange and terrifying sound on my way to the church for the harvest. I saw bodies and flesh scattered in the cornfield," the churchgoer told Reuters.

Billene Seyoum, spokeswoman for the Prime Minister's Office, Oromiya regional spokesman Hailu Adugna and military spokesman Colonel Getnet Adane did not immediately respond to requests for comment.

Badassa Lemessa, head of the local office of the state-appointed Ethiopian Human Rights Commission (EHRC), said it had received reports of the attack and was investigating.

A second resident of the area who witnessed the attack said the group was most probably killed by a drone strike. 

"It wasn't a helicopter. We couldn't see it. It was very far away and the sound was like a drone," the second witness said.

The OLA is an outlawed splinter group of the Oromo Liberation Front (OLF), a formerly banned opposition party that returned from exile after Prime Minister Abiy Ahmed took office in 2018.

Its grievances are rooted in the alleged marginalisation and neglect of people in Oromiya. The OLF also blamed Monday's deaths on a drone strike.