North Korean leader Kim Jong-il (right) inspects the Kim Chaek iron and steel complex with his third son and heir-apparent Kim Jong-un Photo: EPA

The Mainichi newspaper printed a photo of a round-faced and well-dressed man accompanying North Korea’s “Dear Leader” on a visit to a steel mill in North Hamgyong Province in March.

Kim Jong-un is being groomed to take over from his father, whom some experts believe to be suffering from the after-effects of a stroke that has been worsened by long-standing diabetes as well as kidney and heart disease.

Little is known of his third son and the last photos confirmed to have been of Kim Jong-un were taken when he was in his early teens. Now believed to be in his late 20s, North Korea’s state-run media has been gradually raising his profile over the last 18 months, since his two other brothers apparently fell out of favour.

Kim Jong-un last week organised the fireworks display along the Taedong River in Pyongyang to mark “The Day of the Sun,” the 98th anniversary of the birth of Kim Il-sung, the founder of the nation and Kim Jong-il’s father.

Kim Jong-il was himself entrusted with the event shortly before assuming a more important role in the Central Committee of the North Korean Workers’ Party.

The lavish fireworks display is estimated to have cost $5.4 million (£3.5 million).

This week, China, North Korea’s closest ally, predicted serious food shortages in North Korea in May due to a poor harvest last year. The regime reportedly requires 2 million tons of corn and other foodstuffs to stave off another famine.