North Korea has officially named Kim Jong Un as supreme commander of its military forces, affirming his authority after his father's death.

The state-run Korean Central News Agency made the announcement Saturday. It said Kim Jong Il's son and successor was given the title at a meeting of the Political Bureau of the Central Committee of the Workers' Party.

Mr. Kim who is in his late 20s has received a string of leadership titles from the government and state media in the wake of Kim Jong Il's death December 17, but few of them were official appointments.

The state-run media say Mr. Kim was made the supreme commander of the 1.2 million-strong military according to his father Kim Jong Il's wish expressed October 8. Last year, Kim Jong Il promoted his son to a four-star general and also gave him the vice-chairmanship of the ruling party's central military commission.

The death of North Korea's strongman as well as reports of his illness a few years ago sparked speculations about possible changes in the communist country. But during the funeral ceremonies Wednesday and Thursday, North Korea's top officials appeared to rally around Kim Jong Un.

And Friday, North Korea's powerful National Defense Commission said that there would be no policy changes under young Mr. Kim. In a televised message the commission also stressed there would be no softening toward South Korea's government after Kim Jong Il's death.

“We declare solemnly and confidently that the foolish politicians around the world, including the puppet group in South Korea, should not expect any change from us.”

The statement declared that the country would never deal with South Korean President Lee Myung-bak, a conservative, who has pursued a hard-line stance against the Stalinist North.

In Seoul, South Korean Unification Ministry spokesman Choi Boh-seon told reporters the Korean peninsula was now in a state of “growing mobility” after Mr. Kim's death.

“As North Korea's top leader died, the mobility in the Korean Peninsula's situation has heightened. The South Korean Unification Ministry's main focus next year is to closely monitor situation changes, and to deal with any changes flexibly, promptly and with initiative, based on our policies.”

The funeral ceremony Thursday ended North Korea's period of mourning. Witnesses say trade, traffic and boat tourism between the North and the Chinese border city of Dandong returned to normal Friday.