North Korea leader Kim Jong Un is in a coma, a former South Korea official claims in the wake of reports that the sister of the hermit state's dictator is now in charge.

Chang Song-min, who served as political affairs secretary for the late South Korea president Kim Dae-jung, claimed late last week that Kim was in a coma but Kim Yo Jong, his sister, was not his official successor despite the power shift. Chang said he "assesses" Kim had fallen into a coma "but his life has not ended," the Korea Herald reported.

The 33-year-old Yo Jong is now widely expected to be in a position to carry out some of her brother's duties. The country hasn't established an assumption of power and the spotlight is now on Yo Jong "as the vacuum cannot be maintained for a prolonged period," Chang said.

Based on reports Seoul's intelligence body held a closed-door briefing with South Korea legislators on a new system of government Kim had formed in which he granted some of his most loyal officials authority to run the country. However, the National Intelligence Agency doesn't think the new setup has anything to do with Kim's health.

Reports of Kim's deteriorating health hit the headlines and in the past few weeks he hasn't made any regular public appearances. The 36-year-old leader has only been seen a few times this year on the heels of rumors in April that he was in critical condition - or had died - after unsuccessful heart surgery.

But the speculation was later disproved when photos released by Pyongyang's state news media showed Kim cutting a ribbon during the launch of a fertilizer facility.

Meanwhile, in an online post, Chang said power can only be handed over by a North Korea leader to another official if the leader was physically incapable of governing as a result of illness or if ousted in a military takeover, the Korea Herald said.