SEOUL — North Korea's leader-in-waiting Kim Jong-un began a visit to China on Friday, according to media reports here, a trip seen as signifying Beijing's approval of the North's succession process.
"Kim Jong-un arrived in China early this morning ... but we don't know where he is now," Yonhap news agency reported, citing a source in Tumen, a northeastern Chinese border city.
A South Korean official said Mr. Kim was not believed to be accompanied by his father, North Korean dictator Kim Jong-il.
"Judging from circumstances, it appears that Kim Jong-un arrived in China early this morning," the news agency quoted an unidentified senior South Korean government official as saying. "It has yet to be seen whether both the father and the son are paying a visit but it is more likely that this is a solo visit by the son. Apparently, his destination is not Beijing."
The elder Mr. Kim has visited China, the North's sole major ally and economic prop, several times.
It is not known whether his youngest son accompanied him on the last trip in August 2010.
Security was tightened around the city and on the bridge over the Tumen River marking the border with North Korea, the Yonhap source was quoted as saying.
The South's unification ministry refused comment.
Kim Jong-il, 69, took power after his own father died in 1994 and is now preparing for a second dynastic succession. Kim Jong-un, about 27, was appointed a four-star general and given senior posts in the ruling Communist Party in September to prepare him for an eventual handover of power.
The elder Mr. Kim apparently speeded up succession plans after suffering a stroke in August 2008.
The Swiss-educated son has accompanied his father on a variety of inspection visits in recent months.
Yonhap said Kim Jong-un was likely to tour Changchun and Jilin as well as Tumen. The agency said there was speculation he may meet Vice Premier Xi Jinping, China's future leader, in Changchun.