The Ethiopian military has seized control of the town of Wikro, 50 km (30 miles) north of the Tigrayan capital, a senior official said on Friday, a day after the government said it was beginning the "final phase" of an offensive in the northern region.
Federal forces have captured Wikro "and will control Mekelle in a few days", Lieutenant-General Hassan Ibrahim said in a statement. Government troops had also taken control of several other towns, he said.
Reuters was not immediately able to reach the Tigray People's Liberation Front (TPLF) for comment, or to verify the statement.
Claims by all sides in the three-week-old conflict between government and TPLF forces have been impossible to verify because phone and internet connections to the region are down and access to the area is tightly controlled.
On Sunday, the government gave the TPLF until Wednesday to lay down arms or face an assault on Mekelle, a city of 500,000 people, raising fears among aid groups of extensive civilian casualties.
Prime Minister Abiy Ahmed accuses Tigrayan leaders of starting the war by attacking federal troops at a base in Tigray on November 4. The TPLF says the attack was a pre-emptive strike.
Abiy, who announced on Thursday that the military was beginning the "final phase" of its offensive, told African peace envoys on Friday that his government will protect civilians in Tigray.
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But a statement issued by the prime minister's office after their meeting made no mention of talks with the TPLF to end fighting.
The statement issued after Abiy met the African Union envoys - former presidents Ellen Johnson-Sirleaf of Liberia, Joaquim Chissano of Mozambique and Kgalema Motlanthe of South Africa - said the government was committed to the "protection and security of civilians".
The statement thanked the envoys for imparting their "wisdom, insights, and readiness to support in any way they are needed" and did not mention any plans for further discussions with them.
The envoys had been sent to Addis Ababa to help mediate in the conflict, something that Abiy had already made clear he did not want.
The prime minister, who won last year's Nobel Peace Prize for ending a two-decade standoff with Eritrea, has said he will not talk to TPLF leaders until they are defeated or give up.
Thousands of people are already believed to have been killed following air strikes and ground fighting. The United Nations estimates 1.1 million Ethiopians will need aid as a result of the conflict.
The bloodshed has sent shockwaves through the Horn of Africa. More than 43,000 refugees have fled to Sudan. TPLF rockets have hit the capital of neighbouring Eritrea.
Reuters was unable to reach the TPLF for comment on Friday morning, but two diplomats said fighting raged in several areas outside Mekelle. A resident said the city itself was quiet on Thursday night. The United Nations says 200 aid workers are in the city.
UN Secretary-General Antonio Guterres stresses the need to ensure the protection of civilians, human rights and aid access and "appreciates the statement by Prime Minister Abiy today reaffirming the Federal Government's utmost commitment to these obligations," UN spokesman Farhan Haq said on Friday.
Finance Minister Ahmed Shide said on Thursday the government was trying to make people in the city aware of the military operation.
"We have made the people of Mekelle to be aware of the operation by deploying military helicopters and dropping pamphlets in Tigrinya and also in Amharic so that they protect themselves against this," he told France24.
Kenneth Roth, executive director of Human Rights Watch, said such efforts were not akin to protecting civilians from harm.
He also said on Twitter that "with evidence mounting of atrocities committed by both sides in Ethiopia's Tigray province, it's essential to send in international investigators now".
Rights investigators and civilians fleeing the conflict say fighters from both sides, including civilian militias supporting more formal security forces, have carried out mass killings. Both the government and the TPLF deny their forces were involved.
Pope Francis renewed a call for an end to the conflict on Friday and for political dialogue to resolve it. A Vatican statement said the pope was praying for the country and appealed to both sides for the protection of civilians.
Abiy's office said on Thursday that authorities were opening a humanitarian access route, but the United Nations said it had no information on that and the region was blocked to aid groups.
Tigrayans, who make up about 6 percent of Ethiopia's 115 million population, dominated the government until Abiy took power two years ago.
Abiy pledged to unite Ethiopians and introduce freedoms after years of state repression that filled jails with tens of thousands of political prisoners. His government also put senior Tigrayan officials on trial for crimes such as corruption, torture and murder. The Tigrayan region saw those trials as discrimination.
Abiy's reforms created more political space but also lifted the lid on long-repressed tensions over land and resources.