Abiy Ahmed, who has declared a state of emergency in the country, called on citizens to “use every weapon and power” to "bury" rebels.
Ethiopians voted last week in regional elections marred by a civil war and inter-ethnic violence.
"The old conflicts that divide us are back," one voter told VICE World News.
Ethiopia’s state-backed Amhara region security forces are attacking people in their own region. The resulting violence has displaced thousands.
Prime Minister Abiy Ahmed has given the Tigray regional forces a 72-hour ultimatum to surrender. So far they haven’t.
Ethiopia was plunged into crisis Wednesday when Prime Minister Abiy Ahmed announced his government had sent in troops to the restive Tigray region.