Ethiopia’s prime minister and military have warned leaders of a separatist movement in the northern Tigray region to surrender within 72 hours, telling civilians in Tigray’s capital to “free themselves” — or face “no mercy.” Human Rights Watch said the threat constitutes a war crime under international law. It’s been nearly three weeks since Ethiopia’s Nobel Peace Prize-winning Prime Minister Abiy Ahmed launched attacks on the Tigray People’s Liberation Front, killing hundreds and forcing some 40,000 refugees to flee into Sudan.