The elder half-brother of North Korea's leader Kim Jong-Un has been told by a top regime official not to criticise the communist state, including its hereditary succession, a report said Saturday.

Kim Jong-Nam, 41, who has lived abroad for years, was given the advice two months ago when he made a brief home visit, the Japanese newspaper Yomiuri Shimbun reported.

Jang Song-Thaek, head of the administration department of the all-powerful Workers' Party, told Jong-Nam to stop making comments to overseas media, including criticising Jong-Un's inheritance of the leadership, the daily said.

The daily said some of its sources were in Macau -- where Jong-Nam has a house.

Jang told him not to comment about "issues concerning the foundations of the regime" including the military, the daily said.

Jong-Nam has lived mainly in China after apparently falling out of favour with his father Kim Jong-Il for trying to enter Japan on a false passport in 2001.

He has since spoken to Japanese and other overseas media with surprising candour on various occasions.

The senior Kim died last December, allowing his youngest son Jong-Un to succeed him as the North's supreme leader, a position he had himself inherited from his father Kim Il-Sung who founded the country in 1948.

Jong-Un is believed to be in his late 20s.

In an email to a Tokyo Shimbun journalist in January, Jong-Nam said: "Anyone with normal thinking would find it difficult to tolerate three generations of hereditary succession."

In an interview last year before his father's death on December 17, he told the same reporter that the reforms needed to avert the collapse of North Korea's economy would lead to the end of its hardline regime.

Jang, the husband of Kim Jong-Il's younger sister, is also vice chairman of the National Defence Commission, a post seen as the second most important in the country.

"Mr Jang is alarmed by the possibility that criticism held by part of the leadership against Jong-Nam will be directed at himself," one source told the Yomiuri.