North Korea is cranking up its official media to dismiss concern about its new leader\'s youthfulness, describing it as a blessing instead of a reason to doubt his credentials to rule. Chosun Sinbo, a pro-Pyongyang newspaper published in Japan, argued on Monday that Kim Jong-Un\'s age is not a cause for concern. \"In Korea, the leader\'s young age is not a source of anxiety but a source of reassurance. People\'s trust in the leader is absolutely firm,\" the paper said. \"Foreign media have been recklessly uttering that Supreme Commander Kim Jong-Un had a short period to prepare as a successor, but in fact, the opposite is true,\" it said. He is believed to be in his late 20s although the regime has never disclosed his exact age. Longtime leader Kim Jong-Il, who died on December 17, had some 20 years to prepare before his own father and founding president Kim Il-Sung died in 1994. In contrast Kim Jong-Il\'s youngest son Jong-Un had only around three years or less to get ready before his father\'s sudden death from a heart attack. In September 2010, he was appointed a four-star general and given senior ruling party posts despite his apparent lack of relevant experience. But Chosun Sinbo said Jong-Un had served for many years, from as early as in the 1990s, as an adviser or military comrade to \"General\" Kim Jong-Il. Rodong Sinmun, daily of the ruling communist party, on January 28 hailed Jong-Un\'s youthfulness. \"Our Supreme Leader, Supreme Commander, is young. It is the Korean nation\'s limitless luck and glory for them to hold high a great young leader who will make the Kim Il-Sung Chosun (Korea) shine all the more,\" it said. It said Jong-Un displayed his mettle as a great military leader when he was a teenager at the Kim Il-Sung Military Academy, astonishing veteran generals. \"He sent chills though the backbones of enemies by commanding bold operations aimed at bolstering the country\'s strength to the utmost such as the launch of satellites and nuclear tests,\" it said. The North in 2009 test-fired a long-range ballistic missile and conducted its second nuclear test, sparking renewed UN sanctions. Official media has reported a series of military inspections by the new leader, and pictured him riding a horse and travelling in a tank, in an apparent attempt to bolster his credentials with the armed forces.