In this photo taken Sunday, April 15, 2012, North Korean leader Kim Jong Un, right, looks over at North Korean People's Army senior officers, Vice Marshal and Vice Chairman of the Central Military Commission Choe Ryong Hae, center, and Vice Marshal and the military's General Staff Chief Ri Yong Ho, left, during a mass military parade in Kim Il Sung Square to celebrate the centenary of the birth of his grandfather, national founder Kim Il Sung in Pyongyang, North Korea. North Korea said Monday, July 16, 2012 it has relieved Ri Yong Ho from all posts because of illness. (AP Photo/Ng Han Guan)

HYUNG-JIN KIM,Associated Press

SEOUL, South Korea (AP) - North Korea's top military official - a key mentor to young new leader Kim Jong Un who served under his father - has been removed from all posts because of illness, state media said Monday in a surprise announcement that shakes the core of the authoritarian country's power structure.

Ri Yong Ho had looked healthy in recent appearances, and his departure fed speculation among analysts that Kim purged him in an effort to put his own mark on the nation he inherited seven months ago when his father Kim Jong Il died. 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. It was not immediately clear who would take Ri's place, and the dispatch did not elaborate on his condition or future.

Daniel Pinkston, a North Korea analyst at the International Crisis Group, was skeptical of the illness claim, in part because of Ri's recent apparent health. He also said Ri won his major promotions at a September 2010 party conference but received none in April, which stirred speculation about the general's 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 state of North Korea's million-man army, one of the world's largest, is studied closely in South Korea, which stations many of its more than 600,000 troops along the world's most heavily armed border, and in Washington, which keeps more than 28,000 troops in South Korea as a deterrent.

North Korea has repeatedly 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 and raised fears of war.

Ri was vice marshal and chief of the General Staff of the Korean People's Army. In 2010, he was promoted to key political posts in the Workers' Party, including 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 be the result of him losing 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."

The dismissal of the top army official is an especially significant move in North Korea. Kim Jong Il elevated the army's role when he became leader after the 1994 death of Kim Il Sung, his father and 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.

In Seoul, Hong Hyun-ik, an analyst at the private South Korean think tank Sejong Institute, said he expected more aging officials to be dismissed in coming weeks, calling the move part of a "generational change."

Political and military shuffles in North Korea are often mysterious, and officials sometimes drop out of sight without explanation. Many top North Korean officials, however, appear to stay in their posts until they fall ill or die. Vice marshal Jo Myong Rok, who held the No. 2 post at the powerful National Defense Commission, died of heart disease in 2010 at age 82.

The robust 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.

The North's state TV and main Rodong Sinmun newspaper also reported about Ri's dismissal. In a photo posted by state media on July 6, a healthy-seeming Ri was shown talking to people who had just moved into new housing in Pyongyang. He was also cited in state media as accompanying Kim to public events as recently as last week.

"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, Delury said, 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.

Ri, though a powerful figure, arrived on the national scene fairly late, 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."

The Korean Peninsula has remained locked in a state of war and divided since a truce in 1953 ended three years of fighting.

Animosity has deepened since a North Korean rocket launch in April that the U.N. called a cover for a test of banned long-range missile technology. North Korea said the launch, which failed shortly after liftoff, was meant to put a satellite into orbit.