North Korea's economy accelerated at its fastest pace in 17 years, despite sanctions over its nuclear and missile programmes.
Gross domestic product grew by 3.9% in 2016 compared with the previous year, according to the Bank of Korea.
The growth stemmed largely from mining and energy, as well as an increase in exports to China.
The US has been urging Beijing to cut trade with Pyongyang as tensions mount over Kim Jong-un's nuclear ambitions.
China is North Korea's only major ally, trading partner and aid donor.
Last week China issued data suggesting trade with North Korea was not as strong as implied by President Trump.
But while Beijing has stopped coal imports from the North, it has continued to trade iron, iron ore and other commodities.
Although North Korea doesn't publish economic data, South Korea's central bank releases GDP figures every year, based on data from its Ministry of Unification and the National Intelligence Service.
The 2016 GDP data is the highest growth rate since the 6.1% recorded in 1999.
And last year's performance is a turnaround from 2015, when the North Korean economy contracted by 1.1% after a fall global commodity prices hit the value of its coal and iron ore exports.
North Korea's people are among the world's poorest with per capita gross national income standing at 1.5 million won ($1136; £874) a year. South Korea's fper capita income is more than twenty times that.
International tensions over North Korea's were ramped up further last week after the test of a long-range missile, which it is believed was capable of reaching Alaska.