File Photo: Clashes erupted late last year between Sudanese and Ethiopian forces over Al-Fashqa. AFP
"In an act that contravenes all laws and customs of war and international humanitarian law, the Ethiopian army executed seven Sudanese soldiers and a citizen who were their captives," the Sudanese armed forces said in a statement late Sunday.
The army said "this treacherous act will not pass", vowing to respond to "this cowardly behaviour".
Relations between Khartoum and Addis Ababa have soured in recent years over the contested border region of Fashaqa, a fertile strip long cultivated by Ethiopian farmers, but claimed by Sudan.
The Al-Fashaqa region, which also borders Ethiopia's troubled Tigray region, has seen sporadic deadly clashes between the Sudanese and the Ethiopian sides over the past years.
Tensions between the two sides especially rose after fighting erupted in Tigray in November 2020, which sent tens of thousands of refugees fleeing into Sudan.
Khartoum and Addis Ababa have since been locked in a tense war of words, trading accusations of violence and territorial violations.
The border dispute feeds into wider tensions in the region, including over Ethiopia's controversial Blue Nile dam.
Sudan and Egypt, both downstream countries, have been pushing for an agreement over the filling and operation of the dam.
In February, Khartoum and Cairo slammed Addis Ababa for unilaterally launching power generation at the Great Ethiopian Renaissance Dam.
* This story was edited by Ahram Online