By Ju-min Park and Joyce Lee SEOUL (Reuters) -North Korean leader Kim Jong Un said his country needed to rapidly expand its nuclear armament and called U.S.-South Korea military exercises an "obvious expression of their will to provoke war,

The United States and South Korea kicked off their annual summertime joint military exercise on Monday, amid efforts by Seoul to improve relations with North Korea.

North Korean leader Kim Jong Un stressed his order of a quick expansion of his forces' nuclear capabilities, citing the annual U.S.-South Korea military exercises, according to the country's state media.