The highly scripted display of the prisoner - identified as Kim Dong-chul, a former resident of Fairfax, Virginia - is certain to escalate tensions with Washington less than two weeks after North Korea sentenced an American student to 15 years in prison with hard labor for allegedly trying to take a sign as a souvenir during a tour.
There was no immediate comment from U.S. officials. But Washington has previously accused North Korea of taking Americans into custody as political pawns in its showdowns with the West over issues such as Pyongyang's nuclear weapons program.
In the North Korean capital, news agencies said Kim was brought before reporters and told them that he had spied for South Korea's intelligence agencies, sought to obtain details of the North's military programs and tried to spread "religious" ideas - a serious crime in the North.
Pyongyang accused Kim of receiving a USB drive and documents containing secrets about North Korea's nuclear and military activities. Kim admitted this in court, the state-run Korean Central News Agency (KCNA) reported. Information is so tightly controlled in North Korea that documents that would not be deemed secret elsewhere could be considered dangerous there.
Kim, wearing a blue suit and at times flanked by security officials, described his alleged acts as "unpardonable" yet appealed for mercy, KCNA reported. He was detained in October, the agency said.
North Korea has held similar events previously in which prisoners made statements that appeared to be pre-vetted by authorities. Some former detainees later said their public statements in the North followed intense pressure and coercion.
Photos posted by KCNA showed Kim bowing and appearing to wipe away tears.
In an interview with CNN in January, the South Korean-born Kim said that he was a naturalized U.S. citizen and had lived in Fairfax before moving in 2001 to the Chinese city of Yanji, a main gateway for trade with nearby North Korea.
In the interview overseen by North Korean officials, Kim said he worked in the Rason-Sonbong special economic zone, just over the border in North Korea, as head of a trade and hotel services company.
South Korea's National Intelligence Service, the country's main spy agency, had no immediate comment after Kim's appearance, the Associated Press reported.
Last week, North Korea's highest court sentenced 21-year-old American Otto Warmbier, a student at the University of Virginia, for allegedly trying to steal a propaganda banner during an organized tour over the New Year's holiday.
But unlike Warmbier, very little is known about Kim.
His American passport, shown to CNN in January, states that he was born in Korea on Aug. 24, 1953. According to reports from Voice of America's Korean-language service, he emigrated to the United States during the 1980s and lived in Fairfax, which has a large Korean population.
But when his marriage ended in 2001, he moved to Yanji, the VOA report said, citing Fairfax pastor Simon Park.
North Korea has sharply boosted its confrontations with the West and its allies after tests of a nuclear device and a long-range ballistic missile earlier this year. This week, North Korea held test-fire drills in response to U.S.-South Korean military exercises.
North Korea is also holding three South Koreans and a Canadian pastor for what it calls espionage and attempts to establish churches to undermine the rule of North Korean leader Kim Jong Un.
Separately, Kenneth Bae, a Korean American missionary who was sentenced to 15 years hard labor but later freed, urged Americans to lobby for the release of Warmbier and Korean Canadian pastor Lim Hyeon-soo, who is serving a life sentence.
Bae was released at the end of 2014 after being held for 18 months. He and another American detainee were turned over to James R. Clapper Jr., director of U.S. national intelligence, who made a rare visit to Pyongyang for the release.
"Every petition you sign and every letter you write to support prisoners being held can make a big difference," Bae said in a statement released by his publisher. Bae's book about his detention will be published in May.
"Ask yourself how you can help. Sign a petition. Write a letter. Call your congressional leaders," Bae said. "Let's stand together with them and show that so many of us care about them and want to see them come home to their families soon."
However, it is not clear that any of the detainees are receiving news from the outside world. Warmbier has not been allowed to contact his parents in Ohio.
