Hidden from even the North Korean public, the youngest son of leader Kim Jong-il has for months been the focus of speculation that he will next lead the impoverished state.

South Korean media reported on Thursday that Kim Jong-un was accompanying his father on a visit to China ahead of a rare meeting next month of the North Korea's Workers' Party, which rubber stamps major policy decisions.

South Koreans watch a television screenshowing a picture of Kim Jong-un, North Korean leader Kim Jong-il's son. Credit:Reuters

The meeting, the first of its kind in more than 40 years, is expected to elect a new leadership, likely giving the junior Kim an official party role and formally initiate the grooming for succession.

Swiss-educated Jong-un, thought to be 26 and whose name in Chinese characters translates as "righteous cloud," is the youngest of Kim's three known sons.