The chief of the North Korean Army's General Staff, Ri Yong-ho, was abruptly relieved of all his posts on Monday. Ri (70), a vice marshal and member of the Politburo's Standing Committee, was considered a staunch pillar of the new military elite.
The state-run KCNA news agency said the Politburo on Sunday decided to dismiss Ri from all posts "because of illness."
Ri had experienced a meteoric rise after new leader Kim Jong-un was named as the successor to his father Kim Jong-il. He was appointed vice chairman of the party's Central Military Commission alongside Kim Jong-un at a party congress in September 2010 and was one of eight officials alongside Kim junior's uncle Jang Song-taek who escorted the hearse carrying Kim Jong-il during his funeral in December.
An artillery expert, he has been fingered as the mastermind of the shelling of Yeonpyeong Island in November 2010.
A North Korean source said Ri seems to have been sacked amid a power struggle that has been waged since Kim Jong-un took power. "Either he did something that incurred suspicion from the Kim family or he was targeted by his opponents for mistakes he made," the source speculated.
A South Korean government source called Ri's dismissal "very unusual" and stressed the need to "watch carefully" for further changes in the North or possible provocations.
Only a week ago, Ri stood at Kim Jong-un's side during a visit to the Kumsusan Memorial Palace to pay respects to nation founder Kim Il-sung on the 18th anniversary of his death on July 8.
It is rare for the Politburo to convene on a Sunday and announce its decision the following day.