Oct 10 (Reuters) - Eritrea asked the UN Security Council on Saturday to take deterrent measures against Ethiopia, according to a letter seen by Reuters, saying Addis Ababa's accusations of an invasion by Eritrean forces amounted to a "declaration of war".
The incursion by Eritrean troops, which Asmara has denied and Reuters could not independently verify, has raised fears of a return to all-out war along Ethiopia's northern border where the two Horn of Africa neighbours have clashed before.
Conflicts elsewhere in the region and tensions across the Red Sea have further raised the stakes.
Eritrean Foreign Minister Osman Saleh said in the letter that the incursion claims were part of an Ethiopian plan to justify a war of aggression. He urged the UN to intervene.
"Eritrea requests the UN Security Council to forcefully condemn Ethiopia's deplorable declaration of war against Eritrea ... and take the requisite deterrent measures against it in accordance with Chapter VII of the UN Charter," he wrote.
Chapter VII allows for measures ranging from sanctions to military action, though Osman did not specify what measures Eritrea was calling for.
Ethiopia itself wrote to Security Council members on Friday, stating that Eritrean troops had advanced up to 60 km (37 miles) inside the northern region of Tigray in recent days. It warned that the presence of foreign troops left Addis Ababa with no option but to defend itself.
Ethiopian Prime Minister Abiy Ahmed's spokesperson did not immediately respond to a request for comment on Saturday.
ETHIOPIAN TROOPS, MILITIA ALLIES MOVE INTO TIGRAYAN CITY
Earlier in the day, Ethiopian government forces and their militia allies entered the Tigrayan city of Adigrat, near the border with Eritrea, three residents said, days after Eritrean troops were pushed back from the strategic city.
A video shared on social media and verified by Reuters showed members of a militia allied with the Ethiopian government walking in the streets of Adigrat, which is located 30 km (19 miles) from the border with Eritrea.
Three Adigrat residents also told Reuters they had seen the Ethiopian army and an allied militia in the city on Saturday morning, with one of the residents saying they saw soldiers on patrol along with military vehicles.
Explosions were reported on Wednesday and Thursday near Adigrat, as the US-based conflict monitor ACLED said Ethiopia used drone strikes against Eritrean forces, who then withdrew from positions near the city.
The explosions continued on Friday, according to an Adigrat resident, who told Reuters they had heard repeated explosions overnight and into the morning several kilometres outside town.
ETHIOPIAN SEA ACCESS A FLASH POINT
Eritrean Information Minister Yemane Gebremeskel said on Friday that Eritrea had shown restraint. He said a 2023 statement by landlocked Ethiopia that it would acquire sovereign access to the sea amounted to declaring a war of aggression against his country.
Ethiopia had access to a coastline for decades until Eritrea gained independence from Addis Ababa in 1993. Ethiopia argues that restoring sea access is an existential issue but has said it would be restored through peace and dialogue.
Ethiopia has accused Eritrea of backing the rebel alliance that has been battling government troops since September 23 in its northern regions of Tigray, Amhara and Afar. Eritrea has denied doing so.
After years of war, Eritrea and Ethiopia made peace in a 2018 agreement that earned Ethiopia's Abiy the Nobel Peace Prize. Eritrea fought in support of Ethiopia’s federal government during a 2020-2022 civil war in Tigray, but relations soured again toward the end of that conflict.
The fighting that broke out last month has been the biggest escalation of violence since the Tigray war, in which hundreds of thousands died.
(Reporting by Nairobi newsroom, Writing by Jessica Donati; Editing by Ammu Kannampilly and Joe Bavier)
