Analysts of North Korean politics are sceptical about the official reason given for the sudden removal of the country's army chief from all his posts.
State media say Ri Yong-Ho has been relieved of his duties because of an illness.
The BBC reports there is widespread scepticism in South Korea about that explanation.
The KCNA news agency said the decision to relieve Mr Ri of his duties came at a meeting of the Workers' Party Central Committee politburo on Sunday. The report made no mention of a successor.
Mr Ri was made army chief three years ago under Kim Jong-il, who died in December 2011 after ruling North Korea for almost two decades.
The army chief regularly appeared at state occasions beside him.
He was also one of seven top officials to accompany the younger Kim as he followed the hearse containing his father's body at his state funeral.
Mr Ri was widely thought to be a figure in the inner circle of the new leader and instrumental in helping him cement his position.
Professor Robert Kelly of Pusan National University told the BBC that the army and Workers' Party are the two primary institutions that bolstered the Kim family dynasty, Kim Jong-un did not serve in either of those two institutions.
'''So his position is very vulnerable because he does not know the generals and colonels who prop up the state,'' said Dr Kelly.