Police in Ethiopia have arrested the former president of the country's Somali region. Abdi Mohammed Omar is expected to be charged with human rights violations, including instigating ethnic and religious violence.

He was forced to step down earlier this month after the federal government deployed troops to the Somali region. The standoff left dozens of people dead.

Human rights groups have long condemned the ex-president's role in commanding a notorious police unit accused of carrying out killings, torture and other violations.

In recent months the unit was implicated in ethnic clashes between Somalis and Oromos, which caused hundreds of thousands to be displaced.