Workers in Seoul's Yongsan ward office wait in a parking garage for an all-clear sign during a recent air raid drill. Concerned about a possible attack by North Korea, the South Koreans hold the drills twice a year.
North Korean leader Kim Jong Un looks at a warhead component being developed for a ballistic missile, at an unidentified location in this undated photo released by North Korea's Korean Central News Agency on March 15, 2016.
Mount Paektu, which sits on the border with China, is known in North Korea as the "sacred mountain of revolution" and considered the legendary birthplace of Kim Jong Il and Korean culture.
A statue of Mozambique's first president, Samora Machel, at a city square in the capital Maputo. The monument is one of many similar statues built throughout Africa by North Korean workers. The United Nations on Wednesday banned the export of North Korean monuments, saying the government was earning hard currency that could be used to advance its nuclear program.
Thomas Trutschel/Photothek via Getty Images
This undated photo released by North Korea's official Korean Central News Agency on Nov. 11 shows North Korean leader Kim Jong-Un at a defense detachment on Mahap Islet.
This undated picture released from North Korea's official Korean Central News Agency on Aug. 4 shows North Korean leader Kim Jong Un delivering a speech at the April 25 House of Culture in Pyongyang.
KCNA Via KNS/AFP/Getty Images
Then-Secretary of State Madeleine Albright and North Korean leader Kim Jong Il toast in Pyongyang on Oct. 24, 2000. The U.S. and North Korea signed an agreement six years earlier to curb North Korea's nuclear activities in exchange for aid, but it collapsed in 2002, during the Bush administration.
Visitors look at the China-North Korea Friendship Bridge across the Yalu River from Dandong, in northeast China. A company operating from Dandong is under fresh sanctions by the U.S.
Greg Baker/AFP/Getty Images
Kim Chol Ho, deputy manager of the Rajin port, in North Korea's Rason Special Economic Zone, looks out at small fishing boats. Despite stepped-up international sanctions, North Korea is still trading extensively with China.
A Chinese flag flies on a boat next to the bridge that spans the Yalu River linking the North Korean town of Sinuiju with the Chinese town of Dandong. Most of North Korea's trade is with China, and much of it crosses the border here.
Mark Ralston/AFP/Getty Images