North Korea's economy shrank last year by the most since the peak of its 1990s famine, as international sanctions make it harder for Kim Jong Un to feed his people while developing nuclear weapons.

Gross domestic product contracted 4.1 percent in 2018, according to estimates from South Korea's central bank. This marks the worst performance since 1997 when a series of droughts, floods and botched economic policies caused a deadly famine. GDP shrank 3.5 percent in 2017.

North Korea's exports plunged 86 percent to just $240 million, while imports fell 31 percent, the Seoul-based Bank of Korea said Friday. About 90 percent of North Korean shipments go to China, the country's biggest ally. China has beefed up its enforcement of sanctions since Pyongyang's sixth nuclear test in 2017.