United Nations (UN) Secretary-General Antonio Guterres on Thursday pushed for an immediate ceasefire and unrestricted aid access in Ethiopia's Tigray region, where he said millions of people needed help and women had suffered "unspeakable violence."

"It is time for all parties to recognize that there is no military solution, and it is vital to preserve the unity and stability of Ethiopia which is critical to the region and beyond," Guterres told reporters in New York.

Ethiopian federal government troops and forces from the Tigray People's Liberation Front (TPLF) have been battling since November in a war that has killed thousands of people, led to a major refugee crisis and ethnic killings, rape as a weapon of war and a humanitarian crisis.

"Humanitarian conditions are hellish. Millions of people are in need. Infrastructure has been destroyed. We have heard first-hand accounts of women who have been subjected to unspeakable violence," Guterres said.

"The spread of the conflict has ensnared even more people in its horror," he said.

In recent weeks, the conflict has spread into two neighbouring regions, Afar and Amhara, displacing about 250 000 more people and raising international concerns about a wider destabilisation of Africa's second most populous nation.

Guterres pushed for the start of an Ethiopian-led political dialogue to end the conflict.