SEOUL, South Korea — North Korea vowed Saturday to uphold with "blood and tears" Kim Jong Il's son as "supreme commander" as the country builds up the untested young man in preparation for a third generation of the Kim family dynasty.

Even as North Korea emphasizes anointed heir Kim Jong Un's bloodline and his family's claims as spiritual protectors of the North Korean people, millions are grieving for Kim Jong Il, who state media said died one week ago of a heart attack. North Korea is in an official mourning period until after Kim's funeral Wednesday and a memorial Thursday.

Footage from Associated Press Television News in Pyongyang showed a throng of North Koreans climbing stairs and placing flowers below a smiling portrait of Kim Jong Il. They placed wreaths neatly in a row as solemn music filled the air, and young uniformed soldiers, their heads shaved, bowed to the portrait with their eyes closed.

A sobbing Jong Myong Hui, a Pyongyang citizen taking a break from shoveling snow, told APTN that she came out voluntarily to "clear the way for Kim Jong Il's last journey."

The Rodong Sinmun — North Korea's main newspaper — said in an editorial Saturday that the country would uphold Kim Jong Un as "supreme commander" with vows made in "blood and tears" before Kim Jong Il.

Two special groups of South Korean civilians will visit North Korea on Monday to pay condolences to Kim, South Korean Unification Ministry spokesman Choi Boh-seon said in a briefing Saturday. One group will be led by the widow of a late former president who held a summit with Kim in 2000 and the other by the wife of a late businessman with ties to the North. They will return Tuesday, and Seoul has said it won't allow any other visits by South Koreans.

Citizens in the capital, Pyongyang, meanwhile, received a special gift from the recently deceased leader: loads of fish. North Korea's state-run media reported that Kim was worried about the supply of fish in Pyongyang, and had looked into the matter the day before he died.

A Korean Central News Agency report said 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."

Hunger and malnutrition are major problems for North Korea's mostly impoverished population, with the United Nations warning that rations are inadequate and the U.S. considering sending food aid. Kim's government has long made military spending a priority under the policy of "songun," or military first.

Official media on Saturday were filled with reports of the fish made available by Kim Jong Il. The Rodong Sinmun showed a photo of a woman covering her mouth in sadness and gratitude as she watched loads of herring and walleye pollack being distributed at a crowded grocery store, where they were piled up in baskets.

North Korea has yet to descend to the depths of famine that killed an estimated 5 to 10 percent of its people in the mid- and late 1990s, but hunger has worsened through the year.

A recent food security and crop assessment by experts from the U.N. Food and Agriculture Organization and World Food Program said health officials reported a 50 to 100 percent increase this year in hospital admissions of malnourished children.

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.

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.

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.

In Pyongyang, the youngest son of Unification Church founder Rev. Sun Myung Moon was seen carrying a wreath as he paid respects to Kim. Moon Hyung-jin, 32, had recently met with senior North Korean officials, and his father maintains links with Pyongyang. It was not clear when Moon, who the church said is an American citizen, arrived in North Korea and whether he was there to solely pay respects. The elder Moon founded the church in Seoul in 1954. It later grew into a worldwide movement.

A group of South Koreans and foreigners, meanwhile, launched balloons carrying hundreds of pairs of socks to North Korea on Saturday, saying they hoped to help North Koreans deal better with frigid winter temperatures. South Korean activists occasionally send balloons containing anti-Pyongyang leaflets to North Korea.

North Korea has also claimed that 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.

"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."

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.

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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 Demilitarized Zone dividing the two sides.

Associated Press writers Sam Kim and Eric Talmadge contributed to this report.