Wrapped up against the biting cold, endless rows of people were shown paying their respects to a 22-metre statue of the late leader and his father on Mansu Hill in Pyongyang, the epicentre of the personality cult surrounding the ruling Kim dynasty.
"Despite the freezing December weather this morning, our heart for him grows warmer and our loyalty becomes stronger," said a commentator on state broadcaster Korean Central TV.
Mourners bowed deeply and laid bouquets of flowers at the foot of the statue of Kim Jong-Il, who ruled the secretive communist nation for 17 years before his death in 2011, when his son Kim Jong-Un became leader.
"In the Marshall, however, we see the General live eternally," she added, in reference to Kim Jong-Un.
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Pyongyang newspaper Rodong Sinmun splashed its pages with pictures of the late leader and articles idolising him, saying in a frontpage banner that Kim would "live forever as the Sun".
Kim Jong-Un, accompanied by top party and military officials, was expected to pay homage at Kimsusan Palace of the Sun, a mausoleum in Pyongyang where the embalmed bodies of his father and grandfather are preserved.
Workers and students have held meetings nationwide to mourn the late dictator and pledge loyalty to his son, according to state media.
The North this week accused the United States of seeking to topple its regime through allegations of human rights abuses, and threatened to hit back with its "toughest-ever counteraction".
The comments came with the UN Security Council due to meet next week to discuss North Korea's rights record amid calls for Pyongyang to be referred to the International Criminal Court for crimes against humanity.
North Korea has in turn asked the UN to investigate the United States after CIA torture revelations last week, which the North called "the gravest human rights violations in the world".