THE body of North Korea's long-time ruler Kim Jong Il was laid out in a memorial palace as weeping mourners filled public plazas and state media fed a budding personality cult around his third son, hailing him as "born of heaven".

Indicating that the leadership transition is on track, Kim Jong Un – Kim's youngest known son and successor – visited the body with top military and Workers' Party officials and held what state media called a "solemn ceremony" in the capital, Pyongyang, as the country mourned.

The Korean people were in "deep sorrow at the loss of the benevolent father of our nation", Ri Ho Il, a lecturer at the Korean Revolutionary History Museum, said. "He defended our people's happiness, carrying on his forced march both night and day," he added.

Still images aired on state television showed the glass coffin holding Kim's body surrounded by his namesake flowers – red "kimjongilia" blossoms. He was covered with a red blanket, his head placed on a white pillow.

The coffin was presented in a room of the Kumsusan Memorial Palace, a mausoleum where the embalmed body of his father Kim Il Sung has been on display in a glass sarcophagus since his death in 1994.

Kim Jong Un entered the room to view his father as solemn music played, state media said. He observed a moment of silence, and then circled the bier, followed by other officials.

Kim Jong Il died of a massive heart attack on Saturday caused by overwork and stress, according to the North's media. He was 69 – though some experts question the official accounts of his birth date and location.

Kim's death and the possibility of a power struggle in a country pursuing nuclear weapons and known for its secrecy and unpredictability have heightened tensions in the region.

With the country in an 11-day period of official mourning, the streets of Pyongyang were quiet, but throngs of people gathered at landmarks honouring Kim.

The state funeral is to be held at the Kamsusan Memorial Palace on December 28.