By Semafor AfricaPhotos: Wikimedia CommonsPresident Paul Biya’s shuffle of key army positions during a two-month absence from Cameroon has stoked fresh speculation about political stability in the cocoa and oil-producing nation. The absence of Biya, who at 93 is the world’s oldest president, has prompted renewed questions about his health. Opposition figures in Cameroon have called for the presidency to be declared vacant because he has not been in the country since June 7 — he is thought to be in Switzerland. “I cannot tell you exactly when President Paul Biya is returning,” Communication Minister René Emmanuel Sadi told RFI. Biya has led Cameroon since 1982 and could remain in office until the age of 100 after securing an eighth term last October.