Mr Kim made a surprise non-appearance in parliament
North Korea's mercurial leader Kim Jong-il has not appeared in public for 47 days, according to South Korean monitors.
The so-called "Dear Leader" was last seen in public on 12 February, when he visited the Russian embassy in Pyongyang.
The secretive Mr Kim often disappears from public view. But his failure this week to attend North Korea's annual parliament session - for the first time in six years - has prompted a flurry of speculation.
Some Korea-watchers suspect he could be holed up with top military officials, possibly at a resort in the country's north, following the war in Iraq.
North Korea - branded by United States President George W Bush as part of the "axis of evil" - fears it could be the US' next target.
According to a high-ranking North Korean defector to the South, Jo Myong-chol, North Korea appeared to be on a war footing.
North Korean military leaders, including Vice-Marshal Jo Myong-rok, Mr Kim's deputy on the National Defence Commission, and Kim Yong-chun, chief of the army general staff, also stayed away from the parliament session, Yonhap news agency said.
However, the reason for Mr Jo's absence may have been illness. Yonhap said on Friday that he was receiving treatment for chronic kidney problems in a Beijing hospital.
South Korean officials at the National Intelligence Service, National Police Agency and Unification Ministry, who monitor Mr Kim's movements, indicated however that the North Korean leader did not appear to be incapacitated or ill, Yonhap said.
South Korean intelligence reports show Mr Kim has been "active" during the last 43 days, Yonhap said.
Mr Kim's disappearance from public view is the longest since February 2001, when he was not seen for 35 days.