Defections from South Korea to North Korea are rare

A South Korean man has defected to North Korea, following in the footsteps of his political parents who also made a high-profile switch of allegiance in the 1980s, according to Pyongyang's state media.

Years of repression and poverty in the reclusive North have led around 30,000 people to flee to its democratic neighbour in the decades since the Korean War, but defections in the other direction are extremely rare.

Choe In-guk -- the son of former South Korean foreign minister Choe Dok-shin, who died in 1989, three years after moving to North Korea with his wife -- landed in Pyongyang on Saturday, reported state-run outlet Uriminzokkiri.

In video footage filmed at an airport and posted by the website on Sunday, the 72-year-old Choe said he had arrived in the North Korean capital "for residency".

"I can't find words to describe my gratitude to the Republic that has embraced me," he said in the clip.

Choe added that he had decided to live in the North to "fulfil the wishes" of his parents.

Seoul's unification ministry said Monday it was not aware of Choe's defection until the report was published, noting it does not track individuals because it "respects freedom of movement".

A small number of South Koreans in economic difficulty have defected to the North in the past, but Pyongyang has repatriated many people as they hold little value for its propaganda platform.

It returned two South Koreans last year, said ministry spokesman Lee Sang-min, without elaborating.

The government doesn't keep a record of the number of South Korean defectors to the North, he added.

Pyongyang, which is under heavy economic sanctions because of its multiple nuclear tests and long-range missile launches, denounces defectors to South Korea as "human scum".

Those who do find their way to the South are an important source for accounts of the regime's brutal treatment of its citizens.

Last week a South Korean general was sacked for a lapse in border security after a fishing boat from North Korea carrying four people managed to cross the intensely monitored sea between the countries and dock undetected.