A Japanese weekly magazine says Kim Jong-chul, the second son of the late Koh Young-hee, appears to be the heir apparent to North Korean leader Kim Jong-il.

According to "Aera Magazine," secret documents it obtained show that the 25-year-old junior Kim had virtually been tapped to succeed the North Korean leader in March of last year.

The report said the North Korean leader had instructed that his second son undertake a six-month course at an elite school of the North Korean Workers' Party.

The news comes on the heels of reports that Koh had died on August 13 of a heart attack following a long fight with breast cancer.

The 62-year-old Kim Jong-il inherited the leadership of the country when his father Kim Il-sung died a decade ago. Three of Kim Jong-il's own sons - two of them birthed by Koh - are believed to be vying to succeed their own father.