NORTH KOREA MOURNS: The body of North Korean leader Kim Jong-il lies in state at the Kumsusan Memorial Palace in Pyongyang.

The people of North Korea's capital have received a special gift from recently deceased leader Kim Jong-il: loads and loads of fish.

North Korea's state-run Korean Central News Agency has reported that Kim was concerned about the supply of fish in Pyongyang, and had looked into the matter the day before he died. North Korea announced on Monday, local time, that he died of a massive heart attack on Saturday.

The report, issued late Friday, said Kim's young son and heir, Kim Jong Un, "took all necessary measures to truck fresh fish to the capital city in time and supply the fish to the citizens, even in the mourning period".

North Korea is in official mourning until after Kim's funeral, on December 28-29.

North Korean media have been flowing with eulogies for Kim Jong-il, who ruled the country for 17 years after the death of his father, North Korea's national founder and eternal President Kim Il Sung. Both Kims were the object of intense personality cults.

With Kim Jong Un poised to extend the Kim family dynasty into an additional generation, North Korea is quickly building the mythology by emphasising his bloodline and the Kim family legacy, from its roots as revolutionaries fighting the Japanese to their spiritual role as protectors of the North Korean people.

The state media has broadcast constant scenes of public mourning, with women and children wailing, soldiers bowing before Kim's smiling portrait and senior officials lining up to view his body, which is on display in a glass case at the same funeral palace where his father's embalmed remains are on view.

North Korea has also claimed Kim's death generated a series of spectacular natural phenomena, creating a mysterious glow atop a revered mountain, cracking a sheet of ice on a lake with a loud roar and inspiring a crane to circle a statue of the nation's founder before perching in a tree and drooping its head in sorrow.

The reports have stressed how the North Korean people are deeply indebted to the largesse of their leaders, despite the deepening political isolation and economic hardship they have faced in recent years, including severe famines and shortages of electricity, food and other necessities.

"Leader Kim Jong-il is always with us as we have respected Comrade Kim Jong Un identical to him," KCNA quoted Song Hye Yong, a 42-year-old woman, as saying as she carried "a bag full of fish in her hand".

The report also quoted Kim Jong Hwa, a saleswoman at a grocery in the central district of the city, as saying she was deeply touched by leader Kim Jong-il's gift of fish to the people.

"All of citizens are deeply moved by his deep care," she said.

Despite initial jitters over possible instability, officials in Seoul and Washington are calling the political transition in North Korea smooth so far. There have been no outward signs of unrest on the streets or unusual troop movements along the borders.

The North, however, is highly sensitive to what it sees as outside threats.

Its government-run website, Uriminzokkiri, has slammed South Korea for putting its military on alert, calling that move an "insult" to a nation in mourning.

The Korean peninsula remains in a state of war because the three-year Korean War ended in 1953 in a truce, not a peace treaty. Tanks and troops still guard the heavily fortified Demilitarised Zone dividing the two sides.