North Korean leader Kim Jong-il is reported to be in hospital.
Japanese Prime Minister Taro Aso told a parliamentary committee on foreign policy on Tuesday that Japan has "information that he is probably in hospital."
He said intelligence reports showed Kim Jong-il is being treated by a French surgeon.
Mr Aso said: "His condition isn't good. But we don't think that he's in a state where he's incapable of making any decisions at all."
The health of Kim Jong-il has been the subject of intense speculation since he failed to appear at a key parade in September.
US and South Korean officials say he may have suffered a stroke, but the North says this is a lie.
Earlier this week, Fuji TV reports that Kim Jong-il was receiving treatment from a French brain surgeon. Footage was broadcast of what it claimed was his eldest son, Kim Jong-nam, entering a Paris clinic for a discussion about his father's health.
South Korean intelligence officials have also said they believe Kim Jong-nam recently travelled to France.
Rumours about Kim Jong-il's state of health began when he missed several important anniversary celebrations.
North Korean officials have consistently denied that their leader is ill.
