US citizen Kim Dong-chul has been sentenced to 10 years of hard labor in North Korea.
Kim Dong-chul, who was born in South Korea, was arrested in October 2015 after being accused of spying.
In March, the 62-year-old had made an apparent confession in Pyongyang in front of reporters, saying he was paid by South Korean intelligence officers.
The US has previously accused North Korea of using its citizens as pawns in a diplomatic game. The North Korean government denies the accusations.
North Korea has previously said Kim Dong-chul had a USB stick containing military and nuclear secrets on him when he was arrested in the special economic zone of Rason.
Kim Dong-chul, who used to live in Virginia, had said he was introduced to South Korean spies by US intelligence officers.
Forced public confessions by foreign prisoners are common in North Korea.
Kim Dong-chul’s imprisonment comes amid a period of high tensions. North Korea has recently conducted a series of missile tests following its fourth nuclear test in January, both of which break UN sanctions.
Pyongyang attempted to launch two mid-range ballistic missiles on April 28 which crashed shortly after their launches, prompting an emergency meeting of the UN Security Council.
It is believed North Korea will attempt a fifth nuclear test soon.
The recent burst in activity is thought to be a ramp-up to a rare party congress due to be held on May 6, where leader Kim Jong-un is expected to consolidate power.