Getachew Reda, a spokesperson for the Tigray forces, said on Tuesday that the TPLF forces "completely destroyed" the army's 21st mechanized division in an assault at Raya-Wahirat led by a former commander of that unit now fighting for the TPLF, which the federal government denied.
The U.N. refugee agency says Ethiopia's growing conflict has resulted in thousands fleeing from the Tigray region into Sudan as fighting spilled beyond Ethiopia's borders and threatened to inflame the Horn of Africa region.
Abiy announced military operations in Tigray on November 4, saying they were in response to attacks on federal military camps orchestrated by the TPLF leadership.
The Ethiopian forces have already seized the cities of Igada Hamus, Adigrat and Axum, as well as the town of Adwa.
"The key problem in the worldwide community's approach to Ethiopia is the assumption of moral equivalence, which leads foreign governments to adopt an attitude of false balance and bothsidesism" between the federal and Tigrayan sides, he wrote in Foreign Policy magazine.
A communications blackout in the region has made claims from both sides hard to verify.
In an unusually public disagreement over the weekend, the current AU chair, South African President Cyril Ramaphosa, backed three high-level envoys for Ethiopia, an initiative the United Nations chief quickly praised for "efforts to peacefully resolve the conflict".
" Together with the rest of Ethiopia, we will work to ensure that all humanitarian needs will be addressed".
"The next decisive battle is to surround Mekele with tanks", a military spokesman told the media.
This new development has been communicated in a statement released by the Ethiopian Prime Minister Mr Abiy Ahmed.
"The United Nations and its humanitarian partners in Ethiopia are urgently calling on all parties to the conflict to comply with their obligations under global humanitarian law and protect civilians and civilian infrastructure, including health facilities, and water systems", said Stephane Dujarric, spokesman for UN Secretary-General Antonio Guterres.
Since the conflict started in November this year, hundreds have been killed and more than 30,000 refugees have fled to neighbouring Sudan.
The UN Security Council is due to hold informal talks on the ongoing conflict in Ethiopia's Tigray region, a sign of growing global concern.
Tigray forces were not immediately available for comment.
The Ethiopian government also disclosed that its forces are now on course to the regional capital, Mekelle, where many believe senior TPLF leaders are presently stationed. They ruled Ethiopia for almost three decades until Abiy was appointed in 2018.
But on Monday a spokesman for an Ethiopian committee handling the conflict, Redwan Hussein, again ruled out negotiations with the TPLF but said the government would meet the AU envoys "as a matter of respect".