Germany's leading weekly says Kim Jong-il's second son, Jong-chul, is the official heir to his father.

Der Spiegel on Monday said Jong-chul's presence at a dinner banquet last month that his father hosted in honor of visiting Chinese President Hu Jintao strongly suggests his designation as heir.

The weekly said Jong-chul attended the dinner after Hu asked to meet the North's next leader.

Rumors that Jong-chul was unfit to take over had spread throughout the North after Pyongyang failed to announce his designation as successor in last month's ceremony marking the 60th anniversary of the Workers' Party

The 26-year-old Jong-chul is the son of Kim's second wife Koh Young-hee, who died in August last year of a heart attack.

Kim Jong-il in 1994 took over after the death of his father Kim Il-sung. Three of the junior Kim's sons two of them from Koh are known to be competing for the leadership.