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 Eritrea 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.
The potential for further widespread atrocities in Northern Ethiopia is alarming.
The staggering human cost of this conflict should shock the world's conscienceand the risk of additional atrocities & loss of life is intensifying, particularly around Shire in the Tigray region.
Recent indiscriminate attacks by the Ethiopian National Defense Forces and Eritrean Defense Forces in Shire, and reports that Eritrean forces may soon take control of civilian population centers, are gravely concerning.
To protect civilians, this offensive must stop.
The conflict has displaced millions of people, and camps for displaced Ethiopians have also fallen under attack. If the ENDF and EDF take control of these camps during this offensive, there is significant risk of further assaults and killings being perpetrated against civilians.
With as many as one million people teetering on the edge of famine, we urge all partiesthe governments of Ethiopia and Eritrea, and the Tigray Defense Forcesto agree to a ceasefire, and call for safe and unhindered humanitarian access and withdrawal of the EDF from Ethiopia.