Seven months ago, he was the guardian figure always at North Korean leader Kim Jong-un's side, a top military official whose experience and position lent the young new ruler credibility with the troops.

Now, Vice Marshal Ri Yong Ho is out, dismissed from several powerful posts because of illness, state media said Monday in a brief surprise announcement just days after he last appeared in public.

Ri did not appear ill in recent appearances, feeding speculation abroad that Kim purged him in an effort to put his own mark on the nation he inherited when father Kim Jong-il died in December. At the same time, there was no sign of discord at Ri's last public appearance at a high-level event, barely a week ago.

The decision to dismiss the 69-year-old from top military and political posts was made at a Workers' Party meeting Sunday, according to the official Korean Central News Agency. The dispatch did not elaborate on his condition or future.

Kim Jong-un's mystery woman

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This woman was photographed standing next to North Korean leader Kim Jong-un and clapping as they watched a performance by North Korea's new Moranbong band in Pyongyang, North Korea. (Associated Press)

A mystery woman’s appearance with North Korea's young new leader is front-page news in South Korea.

South Korean media are speculating that the young woman could be Kim Jong-un's younger sister or wife.

North Korean TV on Sunday showed a woman in a black jacket and skirt bowing with Kim at a ceremony marking the 18th anniversary of the death of his grandfather, North Korean founder Kim Il-sung. She is believed to be the same woman shown earlier this month seated next to Kim at a concert. The North's Rodong Sinmun newspaper Monday ran a photo of Kim and the woman on its website. But North Korea released no details about her.

On Tuesday morning, the official Korean Central News Agency announced that a successor had been named. He is Hyon Yong Chol.

The appointment was made by the Central Military Commission of the Workers' Party of Korea and the National Defence Commission of North Korea, the agency said.

Daniel Pinkston, a North Korea analyst at the International Crisis Group, was skeptical of the illness claim. He noted that Ri won his major promotions at a September 2010 party conference but received none in April, stirring speculation about his future.

"There's a very high probability that it wasn't health issues, but that he was purged," sending a strong signal to anyone seeking to challenge Kim Jong-un — even if Ri never directly defied the new leader, Pinkston said.

The dismissal comes as Kim makes waves in other ways. State TV showed him appearing at a music concert and visiting a kindergarten recently in the company of a mysterious woman who carried herself much like a first lady. Her identity has not been revealed but her public presence was a notable change from Kim Jong-il's era, when his companions were kept out of state media.

The dismissal of the top army official is a significant move in North Korea. Kim Jong-il elevated the army's role when he became leader after the 1994 death of father Kim Il-sung, the nation's founder.

Kim Jong-un has upheld his father's "songun" military-first policy, but in April he also promoted younger officials with economic backgrounds to key party positions in line with his push to build up the nation's economy.

1 of world's largest armies

Where Ri's departure leaves North Korea's million-man army, one of the world's largest, remained unanswered.

The Korean Peninsula has remained locked in a state of war and divided since a truce in 1953 ended three years of fighting. North Korea has threatened in recent months to attack South Korea's president and Seoul's conservative media, angry over perceived insults to its leadership and U.S.-South Korean military drills that Pyongyang says are a prelude to an invasion. A North Korean artillery attack in 2010 killed four South Koreans.

The United States said Monday that without fundamental change in policy direction, personnel changes in North Korea's military leadership would mean little. State Department spokesman Patrick Ventrell said North Korea should "take the path available to it" and rejoin the international community by refraining from threats and complying with its international obligations including on denuclearization. He urged the North to feed and educate its people rather than pour "scarce resources into nuclear, missile and other military programs."

Ri was vice marshal and chief of the general staff of the Korean People's Army. In 2010, he won top spots on the Central Military Commission of the Workers' Party and the Presidium of the party's influential Political Bureau. That boosted him to the highest political circles — along with Kim Jong-un, Kim's uncle Jang Song Thaek and other trusted members of Kim Jong-il's circle of advisers.

Ri had been at Kim's side since the young man emerged publicly as Kim Jong-il's successor in 2010, often standing between father and son at major events. He was among the small group of men who accompanied Kim Jong-il's hearse through snowy Pyongyang during the funeral procession.

In the months after Kim Jong-un took power, he accompanied the new ruler on his first trips to visit military units in a pointed show of continuity and military support as Kim sought to shore up the backing of the nation's troops.

Ri's departure could mean he lost a power struggle with rising star Choe Ryong Hae, the military's top political officer tasked with supervising the army, said Koh Yu-hwan, a professor at Seoul's Dongguk University.

Choe, originally a Workers' Party official, was handed several top jobs and was named a vice marshal in April. Ri had been anointed as Kim's patron during the young man's rise to power, Koh said. "But after Kim formally took power, Choe has emerged as No. 2."

Military reshuffles are mysterious

North Korea's political and military reshuffles are mysterious, with officials sometimes dropping out of sight without explanation. Many top North Korean officials — such as Vice Marshal Jo Myong Rok, who died of heart disease in 2010 at age 82 —stay in their posts until they die.

The robust, stocky Ri, who had served as chief of the general staff since 2009, showed no sign of illness when he spoke in late April at a meeting of top officials marking the 80th anniversary of the army's founding. He was shown in photos on July 6 chatting with Pyongyang residents and two days later joined Kim Jong-un at the Kumsusan mausoleum to pay respects to Kim il-sung.

"Whether because of a physical malady or political sin, Ri Yong Ho is out, and Pyongyang is letting the world know to not expect to hear about him anymore," said John Delury, an assistant professor at Yonsei University's Graduate School of International Studies in South Korea.

It's too early to determine "whether Ri's stepping down is a manifestation of civil-military tensions, or Kim Jong-un's attempt to consolidate control" over the army, he said.

Ri, though a powerful figure, arrived on the national scene during Kim Jong-il's final years, Delury said. "Perhaps he was always meant to be a transitional regent figure, and his function is played."