Kim Jong-Un at least "on the surface" appears to be in control of North Korea, South Korea's Defense Minister Han Min-Koo said Thursday after holding talks with US Defense chief Chuck Hagel.

Han offered a carefully measured assessment when asked whether he believed Kim, who returned to the public eye earlier this month after dropping out of sight for nearly six weeks, was fully in command of the nuclear-armed, totalitarian state.

"On the surface it seems that Kim Jong-Un is effectively exercising control" of North Korea, Han told reporters at the Pentagon.

"However its diplomatic isolation and its chronic economic crisis will in the long term increase instability," he added.

Han and Hagel met as part of the 46th annual Security Consultative Meeting, during which the two sides discussed amplifying military cooperation.

Kim made two appearances last week, both notable for the photographs showing him using a walking stick, backing up reports that his disappearance was the result of a leg injury or condition.

His withdrawal, which began in early September, quickly became a source of rumor and speculation, which went into overdrive after he missed two noteworthy political events he would normally have been expected to attend.