TOKYO -- The powerful uncle of North Korea's new leader Kim Jong-un has advised Kim's half-brother Kim Jong-nam not to criticize the country, a news report said Saturday.

Jang Song-thaek told Kim Jong-nam to refrain from making comments critical of the power succession to foreign media, Japan's Yomiuri newspaper reported from the southern Chinese city of Guangzhou, citing an unidentified source on North Korean affairs in Macao.

Kim Jong-un took over the communist country following the December death of his father, longtime leader Kim Jong-il, marking the second hereditary power transfer in the North. The late Kim also inherited power upon the 1994 death of his father, the country's founder Kim Il-sung.

Jang, who has long been considered a key official in helping the new leader consolidate power, gave the recommendation to Kim Jong-nam during Kim's trip to Pyongyang in May, the Yomiuri newspaper said.

Still, Jang is believed to be on good terms with Kim Jong-nam, who has expressed doubts about his younger brother's grip on power.

Jang, who is married to the late leader Kim Jong-il's younger sister, Kim Kyong-hui, is believed to be wielding a strong influence in state affairs as he serves as vice chairman of the powerful National Defense Commission, once headed by the late Kim.

In January, Kim Jong-nam told the Tokyo Shimbun in an e-mail that he had "doubts about how a young successor with some two years (of training as heir) can retain the 37 years of absolute power" wielded by his late father.

Kim Jong-nam also said "it is difficult to accept a third-generation succession under a normal reasoning" process.

Kim, believed to be in his early 40s, has made critical comments to mostly Japanese media in recent years. He has been reported to enjoy a lavish lifestyle in the Chinese enclave of Macao after apparently falling out of favor with his father for attempting to enter Japan on a fake passport in 2001.(Yonhap)