Updated

The next leader of North Korea from the only ruling family the isolated nation has ever known made his public debut Sunday, clapping and smiling as tanks and long-range missiles rolled past in what was said to be the largest military parade staged by the communist state.

Two weeks after he was made a four-star general and set on the path to succession, Kim Jong Un sat next to his father, current North Korean leader Kim Jong Il, and waved from an observation platform to a raucous crowd cheering below.

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EDITOR'S NOTE: AP Seoul Bureau Chief Jean H. Lee and photographer Vincent Yu were among a small group of foreign journalists allowed into North Korea for events surrounding the 65th anniversary of the founding of the ruling Worker's Party and the anointment of Kim Jong Un as the nation's next leader.

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The celebration marked the 65th anniversary of the ruling Workers' Party of Korea but also served as a coming-out party for the younger Kim, designed to introduce the heir-apparent to the people and burnish his image as the next leader, outside experts said.

"The parade served as a sign that the military has loyalty to the successor," said Kim Yong-hyun, an expert on North Korea at Seoul's Dongguk University.

The question of who would lead the nuclear-armed nation of 24 million had arisen after Kim Jong Il reportedly suffered a stroke in 2008. His third son, the Swiss-educated Kim Jong Un, emerged as the heir apparent despite his youth and inexperience.

Dressed in a dark blue civilian suit, the younger Kim watched over a plaza named for his grandfather, North Korea's founder Kim Il Sung, who led his nation during the 1950-53 Korean War.

Thousands of troops from every branch of the 1.2 million-member military goose-stepped to the accompaniment of a military brass band while citizens waved plastic bouquets.

Trucks loaded with katyusha rocket launchers rolled by, but they were dwarfed by a series of missiles, each larger than the last and emblazoned with: "Defeat the U.S. military. U.S. soldiers are the Korean People's Army's enemy."

"If the U.S. imperialists and their followers infringe on our sovereignty and dignity even slightly, we will blow up the stronghold of their aggression with a merciless and righteous retaliatory strike by mobilizing all physical means, including self-defensive nuclear deterrent force, and achieve the historic task of unification," Ri Yong Ho, chief of the General Staff of the North Korean army, said at the event.

Japanese broadcaster NHK reported that the parade included three never-before-shown types of missiles and launching devices, including one thought to be a new Musudan ballistic missile with a range of up to 3,100 miles (5,000 kilometers), capable of hitting Japan and Guam.

South Korea's Defense Ministry said it could not immediately comment on the report, and a call to South Korea's top spy agency seeking comment went unanswered Sunday.

Just days earlier, the world got a first glimpse of the son from photos published in a state newspaper. Sunday's appearance was carried live by state TV, beaming him into North Korean households and giving the people their first good look at the future leader.

The sight of the two Kims side by side, later waving to the crowd above a huge portrait of the late dynastic founder Kim Il Sung, drew cheers of "Hurrah!" and tears from North Koreans attending the parade in the heart of the capital Pyongyang. Some 300,000 people packed the streets to see the parade, the state-run Korean Central News Agency said.

"Kim Jong Il! Protect him to the death!" ''Kim Jong Il, let's unite to support him!" they chanted as the 68-year-old leader walked the length of the platform, appearing to limp slightly and gripping the banister.

The Kims later also appeared at an evening gala featuring fireworks at Kim Il Sung Plaza, which was transformed into a massive set filled with tens of thousands of dancers with Pyongyang's iconic Juche Tower as a backdrop.

The theatrical multimedia performance, combining dance with archived footage shown on two huge screens, was designed to remind the people of Kim Il Sung's role in building the nation from the ashes of the Korean War, and to instill pride in Kim Jong Il's skill in leading the country and ruling party. Footage was shown off homegrown achievements, including the long-range rocket launch that was widely condemned by international powers in 2009.

"If Kim Il Sung could see us now, he'd be so happy," one slogan projected onto Juche Tower read.

"Hurrah! Hurrah!" the dancers shouted at the end, all eyes trained on the veranda where Kim Jong Il was watching the performance with his son and top officials. He appeared and waved to the performers, leaving many sobbing with emotion.

The government allowed international journalists to capture the debut of the man dubbed the Young General after more than two years of virtually closing its borders to foreign media. Select media outlets were given front-row seats at events where the Kims appeared.

His age has never been revealed by North Korean officials, but the South Korean government believes the younger Kim to be 26, born Jan. 8, 1984. On Sunday, he was poised in public, every inch his father's son in both looks and demeanor as he joined Kim Jong Il in raising a hand to salute the troops parading past.

Meanwhile, activists protested the succession plan along the southern side of the Demilitarized Zone dividing the two Koreas.

"North Koreans," read one banner, "wake up and resist the people's murderer Kim Jong Il's shameful three-generational hereditary succession of power."

Activists also sent some 20,000 leaflets packed with $1 bills and CDs carrying anti-Kim Jong Un rap songs floating attached to balloons across the border in hopes of reaching ordinary North Koreans, according to Park Sang-hak, a defector who now lives in Seoul.

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Associated Press writers Kwang-tae Kim and Tomoko A. Hosaka in Seoul, South Korea, and Suhjung Kang in Paju, South Korea, contributed to this report.