Pyongyang, Dec 19 (IANS): North Korean leader Kim Jong-il died Saturday during a train journey "from a great mental and physical strain". He was 69, the country's official KCNA news agency reported Monday.

Kim died "from a great mental and physical strain at 08.30 Dec 17, 2011, on train during a field guidance tour", said the report.

Kim, who had received medical treatment for his cardiac diseases for a long period, suffered "an advanced acute myocardial infarction, complicated with a serious heart shock", on the train, reported Xinhua.

The report said that every possible first-aid measure was taken immediately, which failed to save Kim's life, adding that an autopsy Sunday "fully confirmed the diagnosis of his diseases".

Kim's death was announced in an emotional statement read out on national television. The announcer, wearing black, said he died Saturday of physical and mental over-work, the BBC reported. .

Kim is believed to have suffered ill health for many years.

In April 2009, North Korea's constitution was amended and now implicitly refers to him as the "Supreme Leader".