The Korean Central News Agency (KCNA) identified a new figure, Jon Chang-Bok, as first vice-minister of the People's Armed Forces Ministry in a report yesterday which detailed Kim's trip to an army food-processing factory.
The People's Armed Forces Ministry is essentially the defence ministry and comes under the control of the powerful National Defence Commission.
KCNA did not say when Jon, a relatively little-known figure, was appointed to the post, but he replaces Vice Marshal Hyon Chol-Hae.
But Jong-Un has reshuffled his military top brass in an apparent attempt to secure his leadership since taking over the reins of power.
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In changes disclosed on Sunday, Jang Jong-Nam, a relatively young field commander believed to be in his mid-50s, replaced hawkish defence minister Kim Kyok-Sik.
Kim Kyok-Sik, appointed six months ago, had been seen as a hardline choice given that he was widely believed to have directed the 2010 shelling of a South Korean border island.
And despite the shake-up, other old-guard figures remain in influential positions in the commission and other leadership bodies.
The changes come as the Korean peninsula emerges from a period of highly elevated military tensions that followed the North's nuclear test in February.