Hundreds of Ethiopians on Monday protested in the capital Addis Ababa against ethnic-based attacks a day earlier.
Police confirmed that 23 people were killed in Sunday's attacks and there was unspecified property damage by an "organized" group in an area known as Burayu.
Police said they were making arrests but did not say the motive or identities of the people who were on a killing and looting spree.
Police said an organized group went out in the town of Burayu town, 25 kilometers (15.5 miles) west of the capital Addis Ababa, killing people and vandalizing property belonging to individuals, most of whom came from the South Ethiopia Peoples' regional state.
They are being sheltered now at a school.
Takele Uma, Addis Ababa's deputy mayor, visited the victims and called the attacks despicable.
He promised that the victims would be taken care of.
But at the prime minister's office, guards fired tear gas to disperse demonstrators who demanded immediate action from the government.
As many as 2.8 million Ethiopians are internally displaced, mainly due to ethnic-based attacks in the country, said a UNICEF report in August.
Source: Anadolu Agency