Chad's new military rulers named Albert Pahimi Padacke as prime minister of a transitional government on Monday a week after President Idriss Deby's battlefield death - an appointment quickly dismissed by an opposition leader.
A military council seized power after Deby was killed as he visited troops fighting rebels on April 19. Opposition politicians have called the military takeover a coup, and one said on Monday the army had no right to pick a premier.
The transition and the wrangling around it is being closely watched in a country that is a key power in central Africa and a longtime Western ally against militants across the Sahel.
The military council headed by Deby's son, Mahamat Idriss Deby, has said it will oversee an 18-month transition to elections.
But it is coming under international pressure to hand over power to civilians as soon as possible. The African Union has expressed "grave concern" about the military takeover, while France and regional powers are pushing for a civilian-military solution.
Padacke served as prime minister from 2016 to 2018, and was seen as one of Deby's allies, despite running against him several times. He came second with 10.3% of the vote in an April 11 election. Deby was declared winner right before he was killed.
Yacine Abderamane, president of the opposition Reformist Party, told Reuters he would not accept Padacke's nomination.
"It is not up to the transitional military council to designate a prime minister in this isolated manner. We want there to be talks between political parties, civil society and other actors in order to reach a consensus," he said.