Japanese media are reporting that the third son and heir apparent of North Korean leader Kim Jong-il is in de facto control of the North Korean military.

The Sankei Shimbun daily says Kim Jong-un, who is most likely to succeed his father, has assumed a post in the North's national defense committee's administrative bureau since April.

The bureau is the highest ranking military training agency in the country and is believed to be directed closely by Kim Jong-il himself.

Sankei says Jong-un has already begun training to take over power, as he has been seen accompanying his father to on-site field inspections.