This picture taken by North Korean's official Korean Central News Agency on Dec. 8 and released Dec. 9 shows North Korean leader Kim Jong Un, center, attending the enlarged meeting of the Political Bureau of the Central Committee of the Workers' Party of Korea in Pyongyang. (KNS/AFP/Getty Images)

North Korea on Monday confirmed its purge of Jang Song Thaek, the uncle of supreme leader Kim Jong Un, saying that he abused drugs, disobeyed orders and worked in secret to build up his base of power.

The North said Jang was relieved of all posts and expelled from the Workers’ Party after a meeting Sunday of top officials in Pyongyang. On Monday afternoon, North Korea’s state-run television showed footage of Jang being led out of the meeting by olive-suited state security members, as hundreds of other party members looked on.

Although the North has previously banished high-level leaders, never has it described their alleged transgressions in such detail, some analysts said. The statement about Jang, released by the state-run news agency, ran nearly 1,400 words and said dissent would not be tolerated under its “monolithic leadership system,” with Kim as the “unitary center.”

The statement came six days after South Korea’s spy agency briefed select lawmakers in Seoul on Jang’s likely removal.

Jang, 67, had been installed as a caretaker for the third-generation power handoff by Kim Jong Il, who died two years ago. Until recently, Jang was one of Kim Jong Un’s closest lieutenants, accompanying him at public events nationwide and last year representing him at a meeting in Beijing with Chinese President Xi Jinping.

Jang’s removal marks the most significant shake-up under Kim Jong Un, and some experts see the unusually vivid account as a public warning against disloyalty.

“This means Kim Jong Un punishes his political rivals more severely than Kim Jong Il,” said Cheong Seong-chang, a senior North Korea analyst at Seoul’s Sejong Institute.

According to the North’s statement, Jang’s crimes ran the gamut. He disobeyed the orders of Kim Jong Un and obstructed the work of previous leaders Kim Il Sung and Kim Jong Il. He tried to build up his power base — one with ideals different from those of the state — and was “double-dealing behind the scene.” In his personal life, Jang was “dissolute and depraved,” as well as corrupt.

“By abusing his power, he was engrossed in irregularities and corruption, had improper relations with several women, and was wined and dined at back parlors of deluxe restaurants,” the North said. “Ideologically sick and extremely idle and easygoing, he used drugs and squandered foreign currency at casinos while he was receiving medical treatment in a foreign country under the care of the party.”

North Korea’s announcement did not say whether Jang had been punished beyond his expulsion from the party. It also did not mention his wife, Kim Kyong Hui, who is Kim Jong Un’s aunt and holds power of her own. Some analysts, including Ken E. Gause, an expert on North Korean leadership at CNA Strategic Studies in Alexandria, Va., say Jang and Kim Kyong Hui have been estranged since the 1990s.

Last week, South Korea’s unification minister, Ryoo Kihl-jae, told lawmakers he did not think Jang has been physically harmed.

In his two years in power, Kim has restocked the middle levels of the Workers’ Party and military with younger members who have vowed their loyalty. But removing Jang is riskier, some analysts say, because he is skilled at building agreement and keeping Kim insulated from contentious decisions.

“Maybe in the near term this maybe enhances Kim Jong Un’s image or the power around him,” Gause said. “But this still, ultimately, can go really wrong. You’ve removed from the center of things a person who knew how the system worked and who was apparently a good consensus-builder.”

Some analysts say Jang was deeply involved in programs that earned foreign currency for the government. He also helped oversee a special economic zone in the port city of Rason aimed at attracting investment from China and Russia.

In addition to removing Jang, North Korea also purged his followers, the statement said, though it offered no additional details. South Korean media reports in recent days said that Jang’s relatives, including the ambassadors to Malaysia and Cuba, were recalled to Pyongyang and removed from their posts. Seoul’s spy agency said that two Jang aides were executed last month.

“Jang and his followers did not sincerely accept the line and policies of the party,” the North said.

Yoonjung Seo contributed to this report.