Growing numbers of troops are reported to be mobilising across Ethiopia to join the fight against Tigrayan rebels in the north of the country.
This could signal that the conflict might be taking a new shape with the involvement of forces from the other regions.
Local media say forces are rallying from the Oromia, Sidama and Southern Nations, Nationalities and Peoples’ (SNNP) regions.
It comes amid calls by Prime Minister Abiy Ahmed and a senior military official, Lt Gen Bacha Debele, for the public to show support for the army and the government.
On Wednesday, the authorities in Amhara – which borders Tigray – announced an offensive, calling up retired soldiers and local militias.
There is concern that an intensification and spread of the fighting will further hinder efforts to deliver aid to hundreds of thousands of people on the brink of starvation in Tigray.
Last week, UN officials said the fighting in Tigray had already resulted in a famine that was affecting more than 400,000 people.