Anyone sharing the name of Kim Jong-un was urged to change it in a directive sent out by the North Korean regime almost four years ago, a report said.

An internal state document obtained by South Korea's KBS TV station contained an "administrative order" from then-leader Kim Jong-il for all party, army and police officials to ensure the directive was carried out.

The order was issued in January 2011, shortly after Kim Jong-un had been effectively anointed as the successor of his father, who died in December of that year.

"All party organs and public security authorities should make a list of residents named Kim Jong-un ... and train them to voluntarily change their names," said the document, extracts of which were aired by KBS.

The directive appeared to maintain an ongoing tradition by the reclusive state's Kim dynasty.

The process involved revising names on official documents, including social security cards and school diplomas.

Officials were also directed to reject birth certificates for any newborns named Kim Jong-un.

"Authorities should make sure that there is no-one making unnecessary complaints or spreading gossip ... regarding this project," it added.

The authenticity of the official directive could not be independently verified.

Seoul's unification ministry declined to comment on whether it was genuine, but one government official noted that Pyongyang was known to have banned citizens sharing the names of founding president Kim Il-sung and his son Kim Jong-il.

"Given the North maintained the policy under the two previous leaders, there is a possibility that it would continue to do so now," the official told AFP.

The Kim dynasty has ruled North Korea for more than six decades with an iron fist and pervasive personality cult.

Park Jin-hee, a North Korean defector working for KBS who obtained the document, said she was sure the 2011 directive had been effectively enforced.

"There is no-one in the North named Kim Il-sung and Kim Jong-il, and there is no doubt the same rule applies for Jong-un," Ms Park, who defected in 2008, told AFP.

In March this year, North Korean male university students were reportedly forced to cut their hair in imitation of Kim Jong-un.

AFP