The presumptive future leader of North Korea has embarked on an official trip to China, South Korean media reported on Friday, although government officials in Seoul could not confirm the visit was under way.

Kim Jong-un, the youngest son of the North Korean dictator Kim Jong-il, traveled Friday morning to Jilin Province, in northeastern China, according to anonymous sources cited by the Yonhap news agency and the Chosun Ilbo newspaper.

North Korea experts have expected that the younger Mr. Kim would make an official visit to China, the North’s principal ally, although the scope and itinerary of the trip were not immediately clear.

The trip was not mentioned by the official North Korean news agency.

“In the past, the pattern is that these trips are only confirmed by the Chinese authorities or the North Korean state media after the visit is over and the schedule of events has been completed,” said a Unification Ministry official in Seoul who was not authorized to speak publicly about the trip. “We have seen the reports about Kim Jong-un’s trip but we cannot confirm that the trip is taking place.”

The size and roster of Mr. Kim’s entourage was not immediately known, although the Chosun Ilbo report, which cited an anonymous government official in Seoul, said he was accompanied by his uncle, Jang Song-taek. Mr. Jang, the husband of Kim Jong-il’s sister, is said to control the day-to-day political affairs of the country.

Kim Jong-un, who is believed to be 28 or 29, first emerged publicly last autumn, when he was given the rank of four-star general along with two significant political posts. He has clearly solidified his position as the heir apparent since then, appearing with his father on public visits to farms and factories and at major political gatherings.

Analysts in Seoul said any official trip to China by the younger Mr. Kim would be seen as Beijing’s tacit acknowledgment of North Korea’s succession plan, even if the visit is brief, limited to northeastern China and without much pomp or ceremony.

“If he doesn’t go to Beijing, that would be significant, suggesting the Chinese don’t want to give him the full, total recognition,” said John Delury, a professor at the Graduate School of International Studies at Yonsei University in Seoul. “I can’t imagine it will be a totally in-the-dark visit, but he’s still not the leader of the country who’s making an official state visit.”

If Mr. Kim’s trip does not take him to Beijing, analysts said, it would be important to see which political, military and economic leaders might travel from the Chinese capital to confer with him — particularly Xi Jinping, who is widely seen as the successor to Chinese President Hu Jintao.

Mr. Delury said he expected that North Korea was “making most of the calls about the choreographing of the trip,” although Beijing has recently been “in a proactive mode diplomatically as it tries to corral everyone into a resumption of the six-party talks.”

The talks, which broke down in 2009, focused on the dismantling of North Korea’s nuclear weapons programs. South Korea, Japan and the United States have been reluctant to agree to a resumption of the talks. Russia, China and North Korea are the other members of the six-party process.