Ethiopian demonstrators hurled stones and scuffled with police during a rally by thousands in the capital on Wednesday.
This happened after a video showed dozens of compatriots being shot and beheaded by Islamic State militants in Libya, witnesses said.
The rally was to show solidarity with families of those killed. Scuffles erupted moments after Prime Minister Hailemariam Desalegn spoke. Witnesses saw several people being detained by police.
Ethiopia has confirmed those killed in the video, posted at the weekend, were its citizens. Family members have so far named two of them.