Ethiopia has told the UN Security Council that it is taking measures in self-defense against Eritrea, accusing its neighbour of sending troops across the border and occupying parts of northern Ethiopia.

In a letter dated Friday, Ethiopian Foreign Minister Gedion Timothewos invoked Article 51 of the UN Charter, which recognizes the right to self-defense, but did not specify the measures being taken. The Associated Press could not independently verify Ethiopia’s allegations.

Eritrea rejected Ethiopia’s justification, accusing it of seeking sovereign access to the Red Sea by force. In its response to the Security Council, Eritrean Foreign Minister Osman Saleh urged the council to condemn what he called Ethiopia’s declaration of war and take deterrent measures.

Tensions have escalated following the expulsion of 10 Eritrean diplomats by Ethiopia and the closure of Ethiopia’s embassy in Asmara. Eritrea announced last week that it was severing diplomatic ties.

Meanwhile, government-allied forces reported advances in Ethiopia’s Tigray region, including the recapture of Adigrat, near the Eritrean border. Residents described severe hunger, closed banks and a lack of medical care.

The renewed fighting has raised fears of a wider conflict in a region devastated by the 2020–2022 war, which researchers estimated killed about 500,000 civilians through violence, famine and the collapse of health services.

The latest escalation has also undermined a 2022 peace agreement, as clashes intensified following an alliance between the Tigray People’s Liberation Front and six other opposition groups seeking to oust Prime Minister Abiy Ahmed.