Japan's benchmark Nikkei 225 index has tumbled nearly 5% after the country's ruling Liberal Democrats chose Shigeru Ishiba, a former defense minister, as the next prime minister.

Former Defense Minister Shigeru Ishiba, a plain-spoken populist, won leadership of Japan’s ruling Liberal Democratic Party in a runoff vote on Friday.

Former Japanese Defense Minister Shigeru Ishiba was elected by the ruling Liberal Democratic Party Friday as its leader and, de facto, the next prime minister.