North Korean leader Kim Jong Un (front) stands on the conning tower of a submarine during his inspection of the Korean People's Army (KPA) Naval Unit 167 in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang June 16, 2014. (Photo by Reuters/KCNA)

South Korean special warfare command soldiers participate in winter military training exercise on January 11, 2012 in Pyeongchang-gun, South Korea. The South Korean troops train in temperatures below -20 degrees celsius to defend the country against any possible attacks from North Korea. (Photo by Chung Sung-Jun/Getty Images)

Azalea, whose Korean name is “Dalle”, a 19-year-old female chimpanzee, lights a cigarette at the Central Zoo in Pyongyang, North Korea on Wednesday, October 19, 2016. According to officials at the newly renovated zoo, which has become a favorite leisure spot in the North Korean capital since it was re-opened in July, the chimpanzee smokes about a pack a day. They insist, however, that she doesn’t inhale. (Photo by Wong Maye-E/AP Photo)

In this photo taken June 3, 2009, a female North Korean soldier looks out from behind a barbed-wire fence around a camp on the North Korean river banks across from Hekou, northeastern China's Liaoning province. North Korea's top court has convicted two U.S. journalists, and sentenced them to 12 years in labor prison, the country's state news agency reported Monday. (Photo by Ng Han Guan/AP Photo)

Uniformed participant dance during a mass rally and parade in the capital's main ceremonial square, a day after the ruling party wrapped up its first congress in 36 years by elevating him to party chairman, in Pyongyang, North Korea, May 10, 2016. (Photo by Damir Sagolj/Reuters)

North Korean women in colorful traditional dresses are surrounded by flower blossoms known as “Kimilsungia” as they wait to guide guests at a flower exhibition in Pyongyang, North Korea, April 14, 2014. The flowers, named after Kim Il Sung, are on display to celebrate the late leader's official birth date of April 15, 1912. (Photo by David Guttenfelder/AP Photo)

This photo released by North Korea's official Korean Central News Agency (KCNA) on June 7, 2012 shows North Korean leader Kim Jong-Un (C) surrounded by members of the Korean Children's Union (KCU) organizations during a joint national meeting to celebrate the 66th anniversary of the KCU organizations at Kim Il-Sung Stadium in Pyongyang on June 6, 2012. (Photo by AFP Photo/KCNA via KNS)

North Korean leader Kim Jong Un, his wife Ri Sol Ju and Song Tao, head of the International Department of Communist Party of China (CPC) Central Committee, applaud with ballet dancers in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang April 17, 2018. (Photo by Reuters/KCNA)