North Korean leader Kim Jong-il has died aged 69 , state media said today .
He died following a heart attack . After hearing about Kimâ€™s death South Korea put its armed forced on high alert and said the country was on a crisis footing . Japan convened a special security meeting .
Another neighbour China , North Koreaâ€™s closes ally and largest trading partner expressed shock at the news of his death .
Kim Jong-un is expected to be the likely successor of his father .