Kim Jong Il's son was identified today as head of a top decision-making body of the ruling Workers' Party, a post that now gives him authority over political as well as military matters in North Korea.
A week after state media reported leader Kim Jong Il's death on December 17, the campaign to install successor Kim Jong Un gained momentum.
On Saturday, state media referred to him as "supreme leader" of North Korea's 1.2 million-strong armed forces and said the military's top leaders had pledged their loyalty to him.
Today, the North's main Rodong Sinmun newspaper said North Korean soldiers are upholding a slogan urging them to dedicate their lives "to protect the party's Central Committee headed by respected Comrade Kim Jong Un."
Kim Jong Il, who state media said died of a heart attack, ruled North Korea as head of three main state organs: the Workers' Party, the Korean People's Army and the National Defence Commission.
His father, North Korea founder Kim Il Sung, meanwhile, remains the nation's "eternal president" long after his 1994 death.
Kim Jong Un, who is in his late 20s and was revealed last year as his father's choice among three sons for successor, is the third generation Kim to rule the nation of 24 million. He was named a vice chairman of the Central Military Commission of the Workers' Party, but was expected to ascend to new military and political posts while being groomed to become the next leader.
Today's reference to his new title was in commentary in the Rodong Sinmun newspaper, the mouthpiece of the Workers' Party. It came as two private South Korean delegations arrived in Pyongyang to pay their respects to Kim Jong Il.
The slogan, which state media had frequently used when rallying support for Kim Jong Il, made clear the son is quickly moving toward leadership of the Workers' Party, one of the country's highest positions, in addition to the military.
Kim Jong Il's funeral is set to take place on Wednesday followed by a memorial service on Thursday.
People continued lining up in central Kim Il Sung Square today, where a massive portrait that usually features Kim Il Sung has been replaced by one of Kim Jong Il, to bow before his smiling image and to lay flowers.
Meanwhile, a private delegation of South Koreans paid their respects to Kim Jong Il's son and heir today during a visit to Pyongyang.
Kim Jong Un has made several high-profile appearances on state TV since his father's death was announced a week ago. His surprise meeting with the South Koreans could be intended to push Seoul to pursue co-operative projects that would give North Korea much-needed aid, analysts said.
The South Koreans paid respects at Kumsusan Memorial Palace, where Kim Jong Il's body is lying in state, and met Kim Jong Un there, Seoul's unification ministry said in a statement.
The delegation was led by the widow of former South Korean president Kim Dae-jung - who engineered a "sunshine" engagement policy with the North and held a landmark summit with Kim Jong Il in 2000 - and Hyundai group chairwoman Hyun Jeong-eun, whose late husband had ties to the North.
Footage from AP Television News in North Korea showed the group being greeted by North Korean officials during a stop at a factory park in the North Korean border town of Kaesong. North Korea sent delegations to Seoul when the women's husbands died.