The Ethiopian government rebuffed an African effort to mediate on Saturday, saying its troops had seized another town in their march towards the rebel-held capital of northern Tigray region.
More than two weeks into Prime Minister Abiy Ahmed's offensive, the government says Tigrayan forces are bulldozing roads and destroyed bridges to hold up the advance on regional capital Mekelle, home to about half a million people.
The Tigrayans have promised "hell" for their advancing enemies. They have denied destroying bridges but were not reachable for comment about ploughing up roads.
Hundreds, possibly thousands, have died and more than 30,000 refugees have fled to Sudan since the conflict erupted on November 4. The fighting has spread beyond Tigray, whose forces have fired rockets at the neighbouring Amhara region and the nation of Eritrea, spurring concern of a wider war and the splintering of multi-ethnic Ethiopia.
Abiy's government has said it will soon reach Mekelle after taking various surrounding towns. On Saturday it said Adigrat had also fallen, about 116 km (72 miles) north of Mekelle.
The Tigray People's Liberation Front (TPLF) rebels said nine civilians had died among heavy casualties in artillery hits on Adigrat.
The government could not immediately be reached for comment, but has previously repeatedly denied targeting civilians.
Assertions on all sides are hard to verify because phone and internet connections have been down since the beginning of the conflict and media are largely barred.
Eritrea denies TPLF allegations it has sent soldiers over the border to back Abiy's offensive against the Tigrayan forces, who are also an old foe of Eritrea's.
On Friday, the African Union bloc appointed former presidents Joaquim Chissano of Mozambique, Ellen Johnson Sirleaf of Liberia and Kgalema Motlanthe of South Africa as special envoys to seek a ceasefire and mediation talks.
Abiy, who won the Nobel Peace Prize last year for a peace pact with Eritrea, aims to capture TPLF leaders before talking.
"News circulating that the envoys will be travelling to Ethiopia to mediate between the Federal Government and TPLF's criminal element is fake," the government tweeted on Saturday.
Abiy accuses the Tigrayan leaders of revolting against central authority and attacking federal troops in the town of Dansha. The rebels say Abiy's government has marginalised and persecuted Tigrayans since taking office two years ago.
Abiy denies that, saying he is seeking only to restore law and order and preserve the unity of Ethiopia and its 115 million people.
Aid workers say the conflict is creating a humanitarian crisis in Tigray, where many among the more than 5 million population were already displaced and relying on food aid even before the conflict.
Satellite images from US-based space company Maxar Technologies showed destroyed buildings lining the main road near Dansha airport, where the government says there was a November 4 surprise attack on federal troops.
The TPLF is popular in its home region and dominated national politics from 1991 until Abiy took office. Abiy's parents are from the larger Oromo and Amhara ethnic groups.
"We will do all that is necessary to ensure stability prevails in the Tigray region and that our citizens are free from harm and want," the prime minister tweeted on Saturday.
Over the border with Sudan, the United Nations is planning for the possible arrival of 200,000 refugees.
"The situation is very dire," said Jens Hesemann, emergency response coordinator for the U.N. refugee agency UNHCR, from the Hamdayet crossing point, appealing for urgent donor aid as he stood before tents and crowds of recently-arrived Ethiopians.
Thousands of refugees in Hamdayet and another crossing point, Luqdi, have been lining up for jerry cans and helpings of cornflour porridge, and putting up makeshift tents under scrubland trees. Many had crowded into boats to cross a river into Sudan.