North Korea said Friday it has executed leader Kim Jong-un’s uncle, who it said plotted to subvert his nephew’s regime, branding him a “traitor for all ages” and a “despicable political careerist and trickster.”

The execution of Jang Song-thaek, former vice chairman of the powerful National Defense Commission, took place the day before, following a special military tribunal. He was found guilty and admitted to “anti-party, counter-revolutionary factional acts,” according to the North’s official Korean Central News Agency.

As the “boss of a modern-day factional group,” Jang committed “such hideous crimes as attempting to overthrow the state by all sorts of intrigues and despicable methods with a wild ambition to grab the supreme power of our party and state,” the KCNA said.

The execution, on top of the revelation of treason charges, spelled a startling end to the fate of Kim’s guardian and mentor, who had been deemed the communist state’s second-most influential man. He was married to the young dictator’s aunt, Kim Kyong-hui, the younger sister of Kim Jong-il.

The unusually detailed announcement came only days after the state media said Jang was dismissed from all posts for an array of crimes including corruption, drug use and gambling, fueling speculation of a forthcoming execution.

Rep. Suh Sang-kee, chair of the National Assembly’s intelligence committee, said Jang was believed to have been shot to death with machine guns, as recently happened to two of his aides, citing a briefing from Seoul’s National Intelligence Service.

Kim Jang-soo, chief of Cheong Wa Dae’s national security office, convened an emergency security meeting early in the day to assess the situation in and around the North with related Cabinet ministers.

“The government is closely monitoring a series of incidents that have recently been unfolding in North Korea with grave concern, and will remain calm yet fully prepared for all possibilities,” Unification Ministry Kim Eyi-do said in a statement after the two-hour session.

The Defense Ministry said it has beefed up the operation of intelligence assets, reinforced the military readiness posture and raised the its crisis management task force to general-level. But no unusual signs have been detected from across the border, it noted.

“Although the (North’s) party-led ruling system may continue, we should be prepared for any miscalculation that could stem from various causes, including competition within the military to show loyalty,” Defense Minister Kim Kwan-jin told lawmakers later in the day.

While the White House and U.S. Department of State unanimously condemned Jang’s execution in an unusual move, China dismissed it as “internal affairs.”

“If confirmed, this is another example of the extreme brutality of the North Korean regime,” the U.S. agencies said in a statement. “We are following developments in North Korea closely and consulting with our allies and partners in the region.”

Chinese Foreign Ministry spokesman Hong Lei said, “We are paying attention to related news reports but have no information on the details of the situation.”

By Shin Hyon-hee and Choi He-suk

(heeshin@heraldcorp.com) (cheesuk@heraldcorp.com)