Concern over Kim's health arose when he failed to appear on September 9 at a military parade in Pyongyang marking the 60th anniversary of the secretive communist country. Kim, 66, was believed to have suffered a stroke, which sparked widespread rumors of a possible leadership change.
However, if Kim Jong-il's illness was so serious, his relatives would have remained in the capital, media observers say.
South Korean newspaper Munhwa Ilbo reported on Wednesday that Kim Jong-nam, 37, Kim's oldest son and the man thought to be his most likely successor, left Pyongyang soon after the 60th anniversary celebrations.
Kim Jong-nam, who lives in China and often visits European countries, usually arrives in the North Korean capital for public holidays and does not stay for longer than a month. This time was no exception.
Another relative - Kim's stepbrother Kim Pyong-il, North Korea's ambassador in Poland - returned to Poland just before the celebration to arrange a reception in the embassy.
Last Wednesday the North Korean leader's deputy denied reports that the leader had collapsed, calling them a "conspiracy."
Media reports said that Kim had been operated on by doctors believed to be from China and France after suffering a stroke in mid-August. South Korea's largest daily, Chosun Ilbo, suggested that Kim could have partial paralysis on one side of his body, although South Korean officials seemed to be convinced that he remained in full control of the country.
Kim Jong-il has ruled North Korea since 1994, when he succeeded his late father Kim Il-sung, the communist state's founder.
