An ultimatum given to Tigray rebels to lay down arms expired on Wednesday, with the Ethiopian armed forces threatening an all out offensive on Mekelle, the region's capital.

There was no immediate word from Tigray People's Liberation Front (TPLF), the region's governing party after the expiry of the deadline at 16:30 GMT on Wednesday.

But the group has rejected an earlier deadline to surrender.

Prime Minister Abiy Ahmed on Wednesday rebuffed growing calls for de-escalation, even as African Union envoys prepared to land in Addis Ababa for meetings.

We asked William Davison, the senior Ethiopia analayst at Crisis Group for his thoughts on what to expect following the expiry of the federal government's ultimatum.