Ethiopian troops and a militia in the country's Amhara region have been mobilizing following a series of attacks by Tigray forces, according to British broadcaster Sky News.
The war that began last November was confined at first to Ethiopia's sealed-off northern Tigray region.
Accounts of atrocities often emerged long after they occurred: Tigrayans described gang-rapes, massacres and forced starvation by federal forces and their allies from Amhara and neighboring Eritrea.
The Tigray forces retook much of their home region in a stunning turn in June, and now the fighting has spilled into Amhara.
Angered by the attacks on their communities and families, the fighters are being accused of targeting civilians from the other side.
Members of a local militia unit in Amhara said the village of Uruga was held by Tigrayan forces for three or four days, during which the local clinic and grain mill were burned down.
"I personally want them to be eliminated," said local farmer Seid Gebreze as he walked through a building reportedly reduced to rubble by the Tigrayans.
"How many animals have we lost, how much livestock have we lost?" he asked. "I am prepared to fight."
The leader of the Shete Lebashoche militia, Jamilu Teferu, insisted that Tigrayan forces wouldn't be able to "break up Ethiopia and put pressure on Amharans."
"If the Tigrayans try to deny our identity or claim our land, I say it's never going to happen," he said.
The Tigray Communication Affairs Bureau said allegations in places like Uruga were "totally wrong" and called for an independent investigation, Sky News reported.
Tigrayan forces have described their offensive as an attempt to break the months-long blockade of their region of some 6 million people, as an estimated 400,000 face famine conditions in the world's worst hunger crisis in a decade.