At least 23 people were killed in a weekend of violence targeting minorities in the ethnic Oromo heartland near the Ethiopian capital Addis Ababa, a police source said.

The unrest followed a mass rally last week marking the return to Ethiopia of the leadership of the exiled Oromo Liberation Front (OLF) group, which had fought an insurgency for self-determination for Oromos, Ethiopia's largest ethnic group.

The incidents are the latest in a spate of attacks carried out along ethnic lines since reformist Prime Minister Abiy Ahmed Ali came to power in April, the first Oromo leader in the ethnically diverse country's modern history.