Ethiopia’s Prime Minister Abiy Ahmed has ordered a military offensive, after an army base was taken over by forces loyal to the regional government of Tigray.
Mr Abiy accused the region’s ruling party, the Tigray People’s Liberation Front (TPLF), of launching the attack.
The attack resulted in “many martyrs, injuries and property damage”, he said in a TV address.
The cabinet has declared a state of emergency in the region for six months.
The national authorities have also shut down electricity, telephone and internet services in Tigray.
Tensions between the government and TPLF, which used to be part of the governing coalition before falling out with Mr Abiy, have escalated in recent months, with both sides accusing the other of plotting to use military force.
On Tuesday, the federal parliament proposed that the TPLF be designated as a “terrorist organisation.”