Kim Jong-Un has been made "Marshal" of North Korea, a title previously held by his late father, Pyongyang said Wednesday, in another sign the young successor of the communist dynasty is tightening his grip on power.

The move followed a reshuffle in which army chief Ri Yong-Ho was removed from his post due to "illness" and the little-known Hyon Yong-Cho promoted to vice marshall paving the way for him to take over as head of the 1.2-million-strong military.

"A decision was made to award the title of Marshal of the DPRK (North Korea) to Kim Jong-Un, supreme commander of the Korean People's Army," the official Korean Central News Agency (KCNA) said shortly after releasing a statement forewarning that an "important report" was imminent.

The decision was jointly made on Tuesday by several top state and party organs, KCNA added. The title of Marshal was held by both Jong-Un's father, Kim Jong-Il, and his grandfather Kim Il-Sung, North Korea's founding father.

Il-Sung was promoted to generalissimo in 1992, two years before his death of a heart attack, while Jong-Il was posthumously promoted to generalissimo in February, after his death in December when Jong-Un took power.

"By donning the mantle worn by the two Kims, Jong-Un is projecting an image as a legitimate successor to the throne and tightening his grip on power," Professor Kim Yong-Hyon of Dongguk University told AFP.

With Hyon promoted to vice marshal on Monday, Jong-Un, who was made a general in September 2010, apparently needed a new rank befitting the supreme commander of the military, Cheong Seong-Chang of the Sejong Institute said.

"This is the only title left for Jong-Un to decorate himself with after he assumed almost all party and army positions," he said.

Analysts said Jong-Un has been purging aged military leaders appointed by his father, including former armed forces minister Kim Yong-Chun and U Dong-Chuk who ran the secret police.

Ri's departure took many observers by surprise, with widespread scepticism over the official reason given, and analysts saying Jong-Un, who is believed to be in his late 20s, was moving to reinforce his control over the military.

"The recent changes are all part of his efforts to speed up generational changes in the military and keep the military on a short leash," said Chang Yong-Seok of the Institute for Peace and Unification.

"Granting Jong-Un the title of the country's Marshal will help allay concerns over his grip on power."

Professor Yun Duk-Min of the Korea National Diplomatic Academy said the military's clout had grown out of proportion under the Songun, or military-first, policy of Jong-Un's father.

It has been actively engaged in farming, fishing and civilian construction projects while controlling most of North Korea's trade, reported to be $6.3 billion last year.

"Attempts were made recently to take profitable business projects away from the hands of the military and return them to the government," a South Korean foreign ministry official said.

"Effective control over the military will be crucial in the North's efforts to improve people's livelihoods," the official was quoted as saying by the Joongang Ilbo daily.

KCNA said North Koreans were filled with joy on hearing the news of Jong-Un's new title.

"The news spread fast throughout the country, brining enormous pride and joy to the whole nation," it said.