At least 10 people were killed in drone strikes on Mekelle, a major city in the northern Ethiopian region of Tigray, in what the EU labelled as endangering "a very fragile hope" of peace.
The attack came after forces in Tigray said they were ready for a ceasefire and would accept an African Union-led peace process.
The conflict between the Ethiopian government and the Tigray People's Liberation Front (TPLF) has displaced millions and killed thousands since late 2020.
"We are talking about, in many ways, trends which echo some of the abuses and the impacts on civilians we had documented in the early stages of this now two-year-long conflict", said Laetitia Bader from Human Rights Watch.
Brussels and the African Union have tried to encourage parties to the negotiating table, but conditions in the region have made diplomatic efforts difficult.
"The abuses didn't stop in the intermediary phase. So there were about five months where there was not active fighting going on," Bader said.
"But there were parts of Tigray which were still under Amhara government forces' control and Eritrean forces were still present in western Tigray zone where, along with Amnesty International, we have documented a 15-month-long campaign of ethnic cleansing going on," she explained.
Watch our interview with Human Rights Watch Horn of Africa Director Laetitia Bader in the player above.