The two countries have previously accused each other of declaring war over Tigray, where Ethiopian government forces are fighting Tigrayan rebels and Eritrea is accused of joining the conflict on the rebels’ side. Eritrea recently sent forces to Tigray, prompting Ethiopia to respond with airstrikes.
"Eritrea calls on the UN Security Council to strongly condemn Ethiopia's deplorable declaration of war against Eritrea and take the necessary deterrent measures," Eritrean Foreign Minister Osman Saleh wrote in a letter to the Security Council.
The escalation in fighting raises fears that a wider war could break out in East Africa.
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