Tigrayan leaders say they will not surrender to Abiy administration as United Nations appeals for an immediate end to clashes in Tigray region that has forced 30,000 people to flee to Sudan.
Ethiopian forces have pushed towards the capital of the rebel Tigray region, ignoring international appeals for talks to end the conflict and denying it was targeting any ethnic group.
Federal troops are locked in a two-week conflict against Tigray's forces, which has killed hundreds on both sides, rocked the Horn of Africa, stirred ethnic frictions elsewhere in Ethiopia, and sent 30,000 refugees fleeing into Sudan.
Prime Minister Abiy Ahmed has billed the offensive as a campaign to restore rule of law in the northern state of more than 5 million people, saying victory would come in days.
He launched the offensive on November 4 after accusing Tigrayan forces of an attack on a government base in the region.
'No ethnicity bias'
Tigrayans who have fled to Sudan have told Reuters that militias from Amhara, the neighbouring state, attacked them because of their ethnicity and that government airstrikes were killing civilians.
Abiy's government denies that.
"The federal government ... denounces, in the strongest of terms, mischaracterisation that this operation has an ethnic or other bias," its task force on the crisis said in a statement on Wednesday.
Aiby, 44, is from the largest ethnic group the Oromo and is both a former military comrade of the Tigrayans. He also served in government with them until he took office in 2018.
'Shifted defence line’
Tigrayans represent about 5 percent of Africa's second-most populous country. Their ethnic group dominated political leadership between 1991 and 2018.
On Tuesday, the government accused rebel forces of destroying bridges connecting the regional capital Mekelle with the rest of the country in attempts to hold back federal troops.
Forces loyal to Tigray's ruling party, the Tigray People's Liberation Front, also destroyed the section of the main road eastwards to Mekelle between the towns of Shire and Axum. Shire was under federal control, the task force said.
Debretsion Gebremichael, elected Tigrayan president in polls that Ethiopia does not recognise, told Reuters in a text message that his forces had fallen back but denied they destroyed bridges.
"We have shifted our defence line and as a result, they get into some towns of South Tigray," he wrote.
"No bridge is blown."
On Tuesday, Abiy warned that a three-day deadline for Tigrayan troops to surrender had expired, paving the way for a military push against Mekelle.
'Ethiopia faces hell in battle'
The rulers of Ethiopia's rebellious Tigray region refused to surrender to federal troops and instead claimed they were winning a war that has exacerbated ethnic fractures in the vast nation and further destabilised the Horn of Africa.
"Tigray is now a hell to its enemies," they said in a statement on the two-week offensive against them.
"The people of Tigray will never kneel."
"The wider world will soon testify the amazing victories achieved by the people and government of Tigray," the Tigrayan statement added.
"Attempting to rule the people of Tigray by force is like walking on a burning flame ... Tigray will be the graveyard of dictators and aggressors and not their playground."