Field Marshal Birhanu Jula, the chief of the general staff of the Ethiopian National Defence Force, on Friday accused Eritrea of mobilising financial support for the Tigray People's Liberation Front (TPLF).
He said that Eritrea and the TPLF would need support from Sudan and Egypt, insinuating external interference, but without explaining further.
The TPLF and Ethiopian federal troops waged war between November 2020 and November 2022, when a peace deal was signed in South Africa.
A caretaker administration seen as loyal to Ethiopian Prime Minister Abiy Ahmed was installed in Mekelle, the Tigray capital.
But tensions remained, with the TPLF manoeuvring for political control in Mekelle.
Over the weekend, TPLF fighters captured the key strategic town of Erebti in the northern Afar region, a commander told the Associated Press on Monday.
He spoke on condition of anonymity because he was not authorised to speak with the media.
An official with the Tigray Peace Force, a breakaway faction of the Tigray rebels now allied with federal forces in Afar, confirmed that the rebels took control of the town although he denied that heavy fighting had taken place.
Doctors Without Borders (MSF) on Monday said that there had been a surge in the number of wounded receiving treatment in the north.
The number of patients in the Korem and Alamata hospitals rose from about 180 to more than 420 in 48 hours.
MSF said that 300 wounded had arrived at northeastern Suhul Hospital last week.
Valerie Browning, the co-founder of the Afar Pastoralist Development Association, told the Associated Press about 150,000 people had been displaced.
Ethiopian federal authorities accused the TPLF of seeking to build an alliance with neighbouring Eritrea to destabilise Ethiopia.
Abiy's push for sovereign access to the Eritrean seaport of Assab has reignited tensions with Eritrea, which shares a border with Tigray.
Abiy also angered Somalia by trying to negotiate access to the sea via the separatist territory of Somaliland.
Eritrea accused Ethiopia of shifting blame for the ongoing conflict.
Eritrean Information Minister Yemane Meskel wrote on X that Ethiopia's pursuit of access to the sea had rattled Eritrea and Somalia while its move to host militia training in support of Sudan's militia had put Ethiopia at odds with its neighbours.
A spokesperson for the Sudanese armed forces in a statement rejected Ethiopia's accusations, saying that Ethiopia was offering support to militias fighting the Sudanese military, an apparent reference to the Rapid Support Forces, which have been battling Sudan's army since 2023.
Eritrean troops fought alongside Ethiopian forces against the TPLF in the 2020-2022 Tigray conflict.
The civilian death toll was estimated by Ghent University researchers to be 500,000, including from violence, famine and the collapse of health services.
