The announcement came in a decree read on state radio on Sunday that also outlined other roles within the country's new unity government.
Self-declared President Michel Djotodia has said he intends to stay on as president until the next elections, which are not due until 2016.
His rebel alliance known as Seleka also was awarded several other essential posts in the government, including the minister of mines and the minister in charge of security and public order.
Djotodia's rebels overthrew President Francois Bozize on March 23 after he had spent a decade in power. He and his family fled to neighbouring Cameroon as thousands of rebels invaded the capital.
