North Koreans pledged loyalty to their new leader at a crowded rally in the capital Tuesday as state media aired footage of Kim Jong Un being cheered by elite troops, in signs of his quickly expanding personality cult.

Hundreds of troops applauded and cheered in the footage shown on state TV -- the first official documentary of Kim -- some jumping up and down, as he approached, also clapping his hands. Soldiers also loudly chanted Kim Jong Un's name in rhythm while clapping their hands.

The visit to the prominent tank division Sunday was Kim's first public activity to be recorded in a state television documentary. A voice-over narrated the footage on state TV while military music played loudly in the background.

The footage showed a relaxed-looking Kim dressed in a dark overcoat and leather gloves. He repeatedly pointed his finger in the air and spoke with ease to military officers as he toured a room that had photos of his father Kim Jong Il.

The younger Kim, in his late 20s, was officially proclaimed supreme commander of the 1.2-million-strong military last week after his father's death. State media frequently aired footage of Kim Jong Il visiting military units, factories and farms.

North Korean media reported Kim Jong Un's visit to the unit the day it happened and later released still images, but the documentary Tuesday was the first video footage showing his activity and interactions with the North Korean troops.

On Tuesday, thousands of people packed Pyongyang's snow-covered Kim Il Sung Square to pledge their loyalty to Kim as he continues to consolidate power. Senior North Korean officials clapped their hands on a balcony above and urged the country to unite around Kim Jong Un, according to footage from Associated Press Television News in Pyongyang.

It wasn't immediately clear if he attended the rally.

Crowds beat drums and carried large national flags as they paraded across the square. Some held placards calling for loyalty to Kim and for efforts to improve the economy.