Guterres is currently on an official visit to Colombia.
"The peace process here in Colombia inspires me to make an urgent appeal to the protagonists of the conflict in Ethiopia for an unconditional and immediate ceasefire to save the country," the UN secretary-general wrote on his Twitter page on late Wednesday.
Meanwhile, Ethiopia's EBC News broadcaster reported that the national armed forces had killed 12 commanders of the Popular Front for the Liberation of Tigray (TPLF) rebels within the past two days.
Earlier in November, the Ethiopian parliament declared a six-month state of emergency throughout the country to protect the population from the rebels of the TPLF who are advancing toward the country's capital Addis Ababa. The developments have prompted several countries to start evacuating their diplomatic missions from Ethiopia.
This week, Ethiopian Prime Minister Abiy Ahmed arrived at the frontline to lead the troops fighting against the TPLF.