(CNN) -- Kim Jong Un has assumed "the supreme commandership" of the North Korean army, state media reported Saturday.
The power was transferred to him on October 8 at the behest of his father, Kim Jong Il, who died this month, said the state-run Korean Central News Agency.
The announcement came a day after prospects for a shift in relations on the Korean peninsula were dashed when North Korea said a change in leadership would not mean a change in policy.
"We solemnly declare with confidence that the South Korean puppets and foolish politicians around the world should not expect any change" from North Korea, the country's National Defense Commission said in a statement reported by KCNA.
That statement came after two days of elaborate ceremonies in Pyongyang that honored Kim Jong Il and underlined the rise of his son and chosen successor, Kim Jong Un, to the position of "supreme leader" of the secretive state.
The nuclear-armed North "will have no dealings with the Lee Myung-bak group of traitors forever," the statement said in an English-language version of the KCNA report. Lee is the South Korean president.
South Korea's Unification Ministry expressed disappointment.
"The ministry finds today's statement regretful," it said. "However, the ministry's basic principle towards easing tensions in inter-Korean relations and resolving problems through dialogues remains still. The ministry hopes North Korea to regain stability in the near future and present constructive attitude."
The North criticized the South Korean government's decision to allow only a select group of private citizens to visit Pyongyang to pay their respects to Kim Jong Il, whose death was announced last week.
Lee's government's "show of enmity" toward North Korea "culminated in its act of blocking south Koreans who wanted to visit Pyongyang to mourn the demise of leader Kim Jong Il," the statement said.
Seoul allowed a group of South Koreans, including a former first lady and a leading businesswoman, to travel to the North earlier this week to express condolences over Kim Jong Il's death.
That move, along with a number of other gestures like expressing condolences to the North Korean people, suggested a slight softening in Lee's government's hardline stance toward Pyongyang.
The North, though, did not appear to be impressed by those efforts, expressing anger Friday that more South Koreans weren't permitted to visit Pyongyang and that groups were allowed this week to release leaflets near the border criticizing North Korean leaders.
It also said that the South's decision to put its military on alert after Kim Jong Il's death created "a war-like atmosphere on the ground and in the seas and air."
In one of the more vehement passages of saber-rattling rhetoric, the defense commission warned of revenge over these perceived misdeeds.
"The veritable sea of tears shed by the army and people" of North Korea "will turn into that of retaliatory fire to burn all the group of traitors to the last one and their wailing into a roar of revenge to smash the stronghold of the puppet forces," the statement said.
Amid concerns over change in North Korean leadership, a top U.S. diplomat plans to travel to the region early next year in the first such talks since Kim Jong Il's death, the State Department announced Thursday.
Assistant Secretary for East Asian and Pacific Affairs Kurt Campbell will "discuss a range of important bilateral, regional and global issues" during his four days in China, South Korea and Japan.
The State Department statement specifically mentioned that the "latest developments related to North Korea" will be on the agenda.