The North's official KCNA news agency said on Saturday that Newman had "masterminded espionage and subversive activities," and accused him of being a "criminal" involved in the killings of civilians.
"He was involved in killings of service personnel of the Korean People's Army and innocent civilians," KCNA said. "He admitted all his crimes and made an apology for them," it added.
KCNA separately published what it claimed was a statement of apology from Newman about his activities during the 1950 to 1952 war.
"During the Korean War, I have been guilty of a long list of indelible crimes against the DPRK (Democratic People's Republic of Korea) government and Korean people," the dispatch read.
Removed from plane
Newman, a retired finance executive, was detained on October 26, when officials took him off an Air Koryo plane that was due to leave the country. The 85-year-old retiree from Palo Alto in California was accused by Pyongyang of attempting to meet surviving soldiers who he had trained during the war, and of entering the country "under the guise of a tourist."
The US State Department has so far refused to publish details of Newman's detention.
Newman's son said his father - a keen traveler - had been eager to return to the country, having spent three years there during the war.
While it remained unclear if North Korea would release Newman, Pyongyang did say that he had agreed to "tell the truth" about the country if he returns to the US.
North Korea has detained at least six Americans since 2009, among them two journalists accused of trespassing and several, some of Korean origin, accused of spreading Christianity. Missionary Kenneth Bae remains detained after more than a year.
rc/jm (AFP, AP, Reuters)