Tigrayan authorities accused Ethiopia's government on Friday of carrying out a drone strike against civilians.
The announcement was made less than 48 hours after the warring parties signed a deal to end two years of conflict.
According to the spokesman for the rebel Tigray People's Liberation Front (TPLF) the target of Thursday attack was the city of Maychew.
The attack by drone was followed by artillery shelling that killed and wounded civilians.
The TPLF claims could not be independently verified. The Tigray region has been under a communications blackout for more than a year.
The agreement between the Ethiopian government and the Tigray rebels was signed this week in Pretoria.
Both parties agreed "to permanently silence the guns" but so far, key details and a clear roadmap are still absent.
Ethiopian Prime Minister Abiy Ahmed, a Nobel Peace Prize laureate, sent troops into Tigray on November 4, 2020 to topple the TPLF, the region's ruling party, in response to what he said were attacks on federal army camps.