The North's KCNA news agency said Merrill E Newman, a former special forces officer, was a mastermind of clandestine operations and had confessed to being "guilty of a long list of indelible crimes against DPRK government and Korean people." (Agencies)
In the patchy video, Newman appears composed and is shown reading aloud from a handwritten statement dated November 9, 2013 in a wood-panelled meeting room. At the end, he bows and places a finger print on the document.
"I realise that I cannot be forgiven for my offensives (offenses) but I beg for pardon on my knees by apologising for my offensives (offenses) sincerely toward the DPRK government and the Korean people and I want not punish me (I wish not to be punished)," Newman, who has a heart rhythm disorder, was quoted as saying by KCNA.
DPRK is short for the North's formal name, the Democratic People's Republic of Korea. One of the world's most isolated states, it nourishes memories of the 1950-53 war with South Korea and the United States to keep its impoverished people distracted and the family of founder Kim Il Sung in power. His grandson, Kim Jong Un, is North Korea's current ruler.
It remains technically in a state of war with the South and with the United States because the 1950-53 conflict ended with a truce, not a peace treaty.
Newman, a pensioner from Palo Alto, California, was pulled off an Air Koryo flight in North Korea minutes before it was due to depart for Beijing on October 26.
His wife, Lee Newman, told CNN earlier this week that her husband went to North Korea to "put some closure" on his time during the US military. It was "an important part of his life," she said.
Newman worked as an "adviser" to a partisan regiment during the Korean War as "part of the Intelligence Bureau of the Command of the US Forces in the Far East," KCNA said in a separate report.
"He is a criminal as he masterminded espionage and subversive activities against the DPRK and in this course he was involved in killings of service personnel of the Korean People's Army and innocent civilians," KCNA said.
Newman, in his statement carried by KCNA, said he trained scores of men in guerrilla warfare against the North, including how to sabotage communications and transport lines and disrupt munitions supply.
"In the process of following tasks given by me, I believe they would kill more innocent people," Newman said in the statement.
Public documents in South Korea and the United States show U.S. officers worked as "advisers" to groups of anti-communist partisans during the Korean War.
These officers trained Korean anti-communist guerilla units to launch attacks behind enemy lines.
Newman belonged to the 8240th Unit, nicknamed the 'White Tigers', said guerrillas who were trained by him.
"We co-operated and helped with each other and fought," Kim Hyeon who lives south of Seoul said in an interview with Reuters. Hyeon remained in touch with Newman after the war and visited him with his family in 2004.
"In the past we couldn't even speak up (about our activities,)" said Kim, who served as a staff officer of the Kuwol Regiment of partisans, referring to the clandestine operations it conducted under Newman's supervision.
Newman's family has appealed to the North Korean government for his release saying they believed "some dreadful misunderstanding" was behind the detention.
"If Newman was with the partisans that may explain his detention," Bruce Cumings, an expert on the Korean War at the University of Chicago, told Reuters.
"The North Koreans would treat someone like that with much more disdain than a regular line soldier or officer in the American forces."
A US State Department spokesman said there was no immediate comment on the news. The State Department had previously refused to provide any details of the arrest other than confirming the detention of a US citizen.
After serving in the war, Newman worked as a manufacturing and business executive before retiring in 1984, according to a biography of him in a February 2012 newsletter from Channing House, his retirement home.
North Korea is also holding another American, Christian missionary Kenneth Bae of Korean decent, arrested last year and sentenced in May to 15 years of hard labour on charges of committing hostile acts against the state.
Newman's family has not commented on the latest developments. Phone calls and email queries to his son, Jeff Newman, a real estate executive in the Los Angeles suburb of Pasadena, were not answered.
KCNA said Newman had asked his guide to help look for any surviving soldiers he would have fought against or their families.
"Shamelessly I had a plan to meet any surviving soldiers and pray for the souls of the dead soldiers in Kuwol Mt during the Korean war," he said.
The North's KCNA news agency said Merrill E Newman, a former special forces officer, was a mastermind of clandestine operations and had confessed to being "guilty of a long list of indelible crimes against DPRK government and Korean people."