At least 23 people have been killed in ethnic violence near Ethiopia's capital.

The violence broke out Saturday after a rally to celebrate the return of the exiled leaders of the Oromo Liberation Front (OLF), a rebel group that recently signed a peace deal with the Ethiopian government.

Reports say organized mobs attacked residents and looted businesses in the Burayu district, located in the Oromia region that surrounds the capital.

Hundreds of people have been displaced as a result of the violence. Officials say more than 70 people were arrested.

Fitsum Arega, Prime Minister Abiy Ahmed's chief of staff, condemned the violence in a statement posted on his Twitter feed Sunday, "These cowardly attacks represent a grave concern to the unity & solidarity of our people & will be met with appropriate response."

The OLF fought the government for decades, seeking self-determination for Oromos, who make up Ethiopia's largest ethnic group and have long felt marginalized by the central government.

More than two years of anti-government protests in the Oromia region helped bring about the resignation of prime minister Hailemariam Desalegn in February, paving the way for Abiy's rise to power. Abiy is the first ethnic Oromo leader in Ethiopia's modern history.