The Ethiopian Human Rights Commission has confirmed the killing of 34 bus passengers by unknown gunmen in the western region of Benishangul-Gumuz.
The region has been under attack recently and there has so far been no known link with the Tigray region.
Conflict between Ethiopia’s government and forces in the country’s Tigray region also escalated, with a rockets attack across the border into neighbouring Eritrea, after claiming Ethiopian soldiers were using an Eritrean airport to attack Tigray.
Ethiopia’s prime minister appeared to deny the accusations in a tweet.
But analysts said the latest attacks mark a major uptick in a conflict which has displaced thousands of civilians.
Ethiopia has been through big changes since Prime Minister Abiy Ahmed came to power in 2018.
Twelve people were killed in an attack in the zone in October, while 15 died in a similar attack in late September.