Tigray residents say food and medical supplies are running out as a massive offensive on the region intensifies.
Cities are being carpet bombed, says Tedros Ghebreyesus, the World Health Organization chief, who is from Tigray.
Civilians are being killed and those wounded cannot be saved because of a siege, he says.
Tigray has been under a blockade for 17 months and fighting has surged since a five-month humanitarian truce collapsed in August. An estimated one million people are at risk of starvation.
The African Union (AU) has joined the chorus of international voices calling for an end to hostilities and a recommitment to peace talks.
On Friday, an aid worker from the International Rescue Committee was killed while delivering emergency food to women and children in the town of Shire, which has come under ferocious bombardment.
The EU’s foreign policy chief Josep Borrell expressed horror at the violence in Shire, often directed at civilians.
Camps for the millions of people displaced by the fighting are also coming under attack, according to Samantha Power, the head of the US’s development agency.
If Ethiopian and Eritrean troops took control of them during the current offensive there was “significant risk of further assaults and killings being perpetrated against civilians”, the US Aid chief said.
“The staggering human cost of this conflict should shock the world’s conscience,” she added.
A resident of Tigray’s main city of Mekelle told the BBC there was almost no food in the city.
He said small amounts of the staple grain, teff, were being sold – at more than three times last year’s price.
Drones are flying overhead constantly, terrifying the population.
He said growing numbers of women were offering to join the rebel forces in the face of the relentless onslaught of Ethiopian and Eritrean troops.
It reflects a growing desperation amongst the Tigrayans who fear they will be crushed in the coming weeks.
So deep is the hatred between the two sides it seems almost inevitable that those who lose will be punished ruthlessly.
Kjetil Tronvoll, a professor in conflict studies at the Oslo New University College in Norway, says World War One tactics are being used by Ethiopia’s and Eritrea’s infantry forces who are pushing “massive human waves” on Tigrayan defensive lines.
The analyst tweeted that in his opinion the world’s biggest ongoing armed conflict was currently not Russia’s attack on Ukraine, but the Ethiopian and Eritrean operation against Tigray.
He suggested that up to one million soldiers were engaged in the offensive.
“The carnage is horrendous. Likely as many as 100,000 have been slaughtered over the last weeks,” he tweeted.