Ethiopian troops reach the Eritrean border town of Zalambessa as diplomats try to avert a wider war

Two armies that fought beside each other four years ago are now facing each other across the same border, and the fighting inside Ethiopia has reached the line between them.

Ethiopian government troops have advanced to Zalambessa, a town of around 15,000 people on the Ethiopian side of the border with Eritrea, according to six sources: four people in touch with residents, a diplomat, and an expert on the conflict in touch with the warring parties. The town was previously controlled by Tigrayan rebels. Witnesses and a conflict monitor said Eritrean troops crossed last week into Zalambessa in support of the rebels, though it was unclear on Tuesday whether Eritrean troops or rebels were still present. A spokesman for a pro government militia did not confirm the army had taken the town, and spokespeople for Ethiopia's military and for Prime Minister Abiy Ahmed did not immediately respond to requests for comment.

Asmara denies any incursion. Eritrea has asked the United Nations to take deterrent measures against Ethiopia and argues that Addis Ababa's accusation of an invasion amounts to a declaration of war. The two governments have traded duelling letters at the UN.

The war underneath the border crisis restarted last month, when a rebel alliance led by the Tigray People's Liberation Front went on the offensive and reignited a conflict that killed hundreds of thousands of people between 2020 and 2022. Eritrean forces fought alongside Ethiopia's federal army in that war. Relations have since collapsed, in part over Ethiopia's declared desire for sovereign access to the Red Sea, which it lost when Eritrea became independent. The government's counter offensive has driven the rebels from a string of towns and forced them north, toward the border, which is how a civil war becomes a state to state crisis. Diplomats are scrambling to avert a wider war in a region already carrying the Sudan war and the Red Sea shipping crisis, and where a broader contagion of violence is the stated fear on every side.