Ethiopia denied on Saturday that talks on the growing conflict in its northern Tigray region were imminent, just hours after three African former presidents were named to help mediate the two-week-old crisis.Ethiopian troops are taking towns and advancing on the Tigrayan capital Mekelle despite resistance from regional forces who have used bulldozers to plow up roads and are putting up resistance, the Addis Ababa government said late on Friday.Tigrayan forces were not immediately available for comment. They said in a broadcast on Friday they were making progress on the southern and northern fronts.Assertions on all sides have been difficult to verify because internet and phone links to the region have been down since the conflict broke out on Nov. 4.A hint of the devastation can be seen in satellite images provided to Reuters by commercial space company Maxar Technologies. Destroyed buildings lined the main road in the town of Dansha, where the conflict broke out, the images showed.Hundreds, possibly thousands of people have been killed, more than 30,000 refugees have fled into Sudan, and Tigrayan forces have fired rockets at Ethiopia's Amhara region and the neighboring nation of Eritrea.The African Union announced late on Friday the appointment of former presidents Joaquim Chissano of Mozambique, Ellen Johnson-Sirleaf of Liberia and Kgalema Motlanthe of South Africa as special envoys."The primary task of the Special Envoys is to engage all sides to the conflict with a view to ending hostilities, creating conditions for an inclusive national dialog to resolve all issues that led to the conflict, and restoring peace and stability to Ethiopia," the AU said in a statement.The Ethiopian government has repeatedly said it will not engage in talks with the Tigray People's Liberation Front (TPLF), which it regards as a renegade administration, pointing to what the government says was a surprise attack the group launched on federal troops in Dansha, sparking the conflict."News circulating that the envoys will be traveling to Ethiopia to mediate between the Federal Government and TPLF’s criminal element is fake," a government taskforce on Tigray tweeted on Saturday morning.On Friday, UN Secretary-General Antonio Guterres told reporters that Ethiopia was not interested in external mediation."Until now, there has not been acceptance by the Ethiopian authorities of any form of external mediation," he said.The government has appointed an alternative interim government to run Tigray when troops take Mekelle. Its new head gave a glimpse of government strategy this week when he hinted at forgiveness for TPLF rank and file - the political party has not been outlawed - and a public relations campaign against the TPLF.The TPLF is extremely popular in its home region and dominated national politics from 1991 until Prime Minister Abiy Ahmed took power in 2018.