Ethiopia's Prime Minister Abiy Ahmed says federal troops have begun the final phase of the operation in the northern Tigray state.

In a statement, he said "great care" would be taken to protect the 500,000 inhabitants of the region's capital, Mekelle, from harm.

He said that thousands of Tigrayan forces and militia had surrendered in the last 72 hours - but Tigray officials are yet to respond to the claim.

KAN's Mark Weiss asked Haggai Erlich, professor emeritus at Tel aviv university, what was behind the war.