By James Pearson and Ju-min Park

SEOUL (Reuters) - North Korea's deputy ambassador in London has defected with his family to South Korea, making him the highest-ranking Pyongyang diplomat ever to flee the isolated regime for the democratic South, South Korea said on Wednesday.

The Unification Ministry in Seoul declined to say when or how Thae and his family arrived, or how many relatives accompanied him.

Thae defected due to discontent with the regime of Kim Jong Un in North Korea and for the future of his child, ministry spokesman Jeong Joon-hee told a news conference. It was not clear in Korean whether Jeong was referring to more than one child.

"We know that Deputy Ambassador Thae is saying that his distaste for the Kim Jong Un regime and yearning for the Republic of Korea's free democratic system and the future of his child are motives for the defection," Jeong said, referring to South Korea, adding that Thae and his family were under government protection.

Impoverished North Korea and prosperous South Korea are technically still at war after their 1950-53 conflict ended in an armistice, not a peace treaty.

The announcement came a day after media report that a high-profile North Korean diplomat, later identified by the BBC as Thae, had defected.

Quoting an unnamed source, South Korea's JoongAng Ilbo newspaper had said the diplomat embarked on a defection journey "following a scrupulous plan" and was in the process of "landing in a third country as an asylum seeker".

An official at the North Korean embassy in London would not confirm the defection on Tuesday, describing reports of the event as "quite sudden".

"If it is appropriate to give a response, then you might hear about our response," the official told Reuters.

Further calls to the embassy went unanswered. Calls to Thae's mobile phone were redirected to a voicemail inbox.

The UK's Foreign and Commonwealth Office did not have an immediate comment after South Korea's announcement.

Thae's defection follows a string of recent such flights by North Koreans, including 12 waitresses at a North Korean restaurant in China who defected to South Korea earlier this year.

Those waitresses have finished a prolonged period of investigation and have entered into normal society, an official at South Korea's Unification Ministry said on Wednesday.

The number of defections by North Koreans to the South this year through July totaled 814, an annual increase of 15 percent, a ministry official told Reuters.

Several diplomats from North Korea have defected to the South over the last two years, including one from Thailand, South Korea's Yonhap News Agency reported on Wednesday, citing a source familiar with North Korean affairs.

Overall, the number of defectors, mostly from the area near North Korea's border with China, has declined since leader Kim Jong Un, a third-generation dictator, took power following his father's death in late 2011.

"The bigger picture is that while there have been fewer total defections per year under Kim Jong Un, there have been a higher number of strategically significant and political defections," said Sokeel Park of LiNK, an NGO which works with North Korean defectors.

North Korea has become increasingly isolated after conducting its fourth nuclear test in January and numerous ballistic missile launches this year, which resulted in tightened UN Security Council sanctions.


Among his many responsibilities, Thae was well-known to the British press, acting as the embassy's main point of contact for British correspondents traveling to Pyongyang.

Thae lived at or near the North Korean embassy, which is in the leafy west London suburb of Gunnersbury. He spoke regularly at far-left events in London, including meetings of a British communist party where he would make impassioned speeches in defense of North Korea, according to videos of the events.

Thae's son, Thae Kum Hyok, who was known as "Kum Thae", was a pupil at Acton High School, a short walk from the embassy. The school term ended on July 22, according its website, around the same time Thae is believed to have defected.

The son, 19, has a place at Imperial College, London, to study maths and computer science, according to one of his school friends cited by the Guardian newspaper.

Debonair and well-spoken, Thae Yong Ho has over ten years experience working on UK and EU-related issues as a diplomat. He is cited in European Parliament archives as a London-based diplomat joining a North Korean delegation to Brussels.

His measured style was a contrast to the bombastic rhetoric often used by Pyongyang's propagandists, although at some events he sang revolutionary Red Army Choir songs in Korean.

In regular contact with the media, Thae also spoke publicly about media coverage of the isolated country, including the press appetite for sensationalist stories about North Korea.

"I don't blame reporters," Thae said during a speech at a left-wing London bookshop in late 2014. "If they broadcast (North Korea) as it is, the editors of these TV stations and newspapers will (change it).

"The more horrifying, the more shocking stories they create, the more they will be viewed by the British public".

According to an online search of his name, Thae's son was an avid gamer, and had accumulated 368 hours regularly playing CounterStrike over the last year, under the name "North Korea is Best Korea".

The account was last active on July 13.

(Addtional reporting by Mike Holden in LONDON and John Walcott in WASHINGTON; Editing by Raju Gopalakrishnan, Tony Munroe and Nick Macfie)