But new GPB director Kim Su Gil was a "highly trusted" lieutenant of leader Kim Jong Un, it added, who appointed him to the Pyongyang party committee - once a powerbase for his uncle Jang Song Thaek - after having the older man executed for treason in 2013.
Kim Jong Un is preparing for a high-stakes summit with U.S. President Donald Trump in Singapore on June 12, the first such meeting between a North Korean leader and a sitting U.S. President.
The United States is seeking a negotiated end to North Korea's nuclear weapons program and US officials believe there was some dissension in the military about Kim's approaches to South Korea and the United States.
It quoted Mr Assad as saying on Wednesday: "I am going to visit [North Korea] and meet Kim Jong-un".
His South Korean counterpart urged support for dialogue to help North Korea join the worldwide community, saying its leader Kim Jong Un must be given the benefit of the doubt. But after meeting with a senior North Korean leader Friday, Trump seemed to walk back that approach.More news: Lava from Guatemala volcano kills at least 7
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The chief of general staff Ri Myong Su has been replaced by his deputy Ri Yong Gil, according to Yonhap which cited intelligence sources.
Mr. Trump wants North Korea to "denuclearize", or get rid of its nuclear arsenal, in return for relief from economic sanctions. North Korea's leadership is believed to regard nuclear weapons as crucial to its survival. "North Korea will receive relief only when it demonstrates verifiable and irreversible steps to denuclearisation", Mattis added.
Kim Yong-hyun, a professor of North Korean studies at Dongguk University in Seoul, said the reported new military leadership brings expertise in military-run economic affairs rather than combat strategies.
Trump on Friday revived the summit after cancelling it a week earlier.
Despite a long-standing security alliance between the United States and Japan, some people in Japan worry that the United States may cut a deal to protect its cities from nuclear attack by the North, while leaving Japan vulnerable.
Madden said any similar attempt to wrest power during the North Korean leader's absence was unlikely, pointing to Kim's previous trips to Beijing and Dalian in China, which went off without a hitch.