North Korea has announced the removal of its military chief, a key advisor to leader Kim Jong-un.

In a surprise radio announcement Monday, the North's official Korean Central News Agency said Vice Marshal Ri Yong-ho had been removed from all of his posts because of illness.

The announcer said the Workers' Party central committee political bureau decided Sunday to remove the 69-year-old of all of his political posts, including the presidium of the politburo, considered North Korea's most powerful body. The announcement made no mention of Ri's position as head of the military.

The short announcement caught officials and analysts in South Korea by surprise. They note Pyongyang rarely removes top figures for health reasons.

Kim Hyung-suk, a spokesman for the Unification Ministry in Seoul, which oversees North-South relations, called the announcement, “very unusual.” He said Seoul has no more to say at this point and is closely monitoring the situation for further information.

Analyst Chon Hyun-joon, a senior researcher at Seoul's state-funded Korea Institute for National Unification, says he believes Ri, a hard-liner, lost a power struggle with moderates. The analyst said this denotes a collapse of one of the supports for the military – the other axis being the political chief of the army.

Chon predicted the change will allow Kim Jong Un to proceed with a more flexible diplomatic policy.

Ri, a third generation member of Pyongyang's elite inner circle, served in top positions under Kim Jong Il. He was one of the eight who walked alongside the late leader's hearse during the December 28th funeral procession.

Ri was last seen in public accompanying Kim Jong Un on July 8th, during a commemoration of the death of the country's founder Kim Il Sung (the grandfather of the current leader).