WRAPUP 3-Son of North Korea's Kim visits China as heir-media

(For full coverage of North Korea, click [ID:nSP431049])

* Kim Jong-il's youngest son on secret China visit -report

* Chinese leaders urge against another nuclear test -report

* South Korean president to meet Obama in Washington (Adds Chinese government spokesman, analysis, Japan sanctions)

By Yoko Kubota

TOKYO, June 16 (Reuters) - The youngest son of North Korean leader Kim Jong-il secretly visited China last week and his hosts were told he had been appointed heir to the ruling family dynasty, Japan's Asahi newspaper reported on Tuesday.

The report, citing unidentified informed sources, said Kim Jong-un met Chinese President Hu Jintao and other leaders of the ruling Communist Party when he flew to Beijing around June 10.

Analysts have said North Korea's nuclear test on May 25 and other belligerent acts may be aimed at a domestic audience, with the elder Kim trying to bolster his position at home to secure the succession of his youngest son. The 67-year-old leader is believed to have suffered a stroke last year. [ID:nSEO120054]

An aide to Jong-un told Chinese officials the younger Kim had been appointed heir and that he held an important post in the ruling Korean Workers' Party, the mass circulation Asahi said.

"If what was said in the paper is proven to be true, it would not be a stretch to say the decision to make him heir is official," said Ko Yu-hwan, a professor of North Korean studies at Seoul's Dongguk University.

A Chinese Foreign Ministry spokesman said he had no knowledge of the reported visit. North Korean state media has never told the country's public that leader Kim has offspring, let alone report on the journey of a son to Pyongyang's key backer.

Jong-un is the Swiss-educated third son of Kim Jong-il and was born in 1983 or 1984. Earlier this month South Korean media, quoting informed sources, said Pyongyang had asked the country's main bodies and overseas missions to pledge loyalty to him, indicating he will take over from his father. [ID:nSEO1264]

China is the closest thing North Korea has to an ally, and in theory Beijing wields more influence over Pyongyang than any other power, but experts say the relationship is brittle and China actually has limited room for manoeuvre.

Hu apparently asked North Korea not to go ahead with another nuclear test or test-fire an intercontinental ballistic missile, the Asahi reported. Jong-un was believed to have asked China for emergency energy and food aid, the newspaper said.

DILEMMA FOR CHINA

Beijing does not want its neighbour to build up a nuclear arsenal that could spark a regional arms race, but nor does it want to risk North Korea falling into chaos -- which could prompt a flood of refugees across their land border.