A senior North Korean diplomat based in London has defected, South Korea has confirmed.

The deputy ambassador, Thae Yong Ho, has arrived with his family in South Korea, making him the highest-ranking diplomat ever to defect to the South.

Mr Thae defected due to his discontent with the regime and for the future of his child, Jeong Joon-hee, a spokesman at the South's Unification Ministry, told a news conference.

Workers' Party Congress in North Korea Show all 12 1 /12 Workers' Party Congress in North Korea Workers' Party Congress in North Korea North Korean leader Kim Jong Un waves to the crowd as he presides over a mass rally and parade in the capital's main ceremonial square, a day after the ruling party wrapped up its first congress in 36 years by elevating him to party chairman Reuters Workers' Party Congress in North Korea North Korean parade participants wave decorative bouquets of flowers and carry their country's national flag as they march with a model of the Unha pace launch vehicle at the Kim Il Sung Square. Hundreds of thousands of North Koreans celebrated the country's newly completed ruling-party congress with a massive civilian parade featuring floats bearing patriotic slogans and marchers with flags and pompoms AP Workers' Party Congress in North Korea People react as they see North Korean leader Kim Jong Un during a mass rally and parade in the capital's main ceremonial square, a day after the ruling party wrapped up its first congress in 36 years by elevating him to party chairman in Pyongyang Reuters Workers' Party Congress in North Korea High party and military officials react as North Korean leader Kim Jong Un appears at the beginning of a mass rally and parade in the capital's main ceremonial square Workers' Party Congress in North Korea North Korean leader Kim Jong Un is accompanied by high party and military officials as he presides over a mass rally and parade in the capital's main ceremonial square, a day after the ruling party wrapped up its first congress in 36 years by elevating him to party chairman, in Pyongyang, North Korea, May 10, 2016. REUTERS/Damir Sagolj Reuters Workers' Party Congress in North Korea North Korean leader Kim Jong-Un waves from a balcony of the Grand People's Study House following a mass parade marking the end of the 7th Workers Party Congress in Kim Il-Sung Square Getty Images Workers' Party Congress in North Korea Attendees cheer the arrival of North Korean leader Kim Jong-Un during the 7th Workers Party Congress Getty Images Workers' Party Congress in North Korea A hostess and security guard stand inside the April 25 Palace, the venue of the 7th Workers Party Congress Getty Images Workers' Party Congress in North Korea North Korean leader Kim Jong Un attends the first congress of the country's ruling Workers' Party in 36 years Reuters Workers' Party Congress in North Korea Party representatives sit in the hall of the April 25 House of Culture during the party congress in Pyongyang AP Workers' Party Congress in North Korea North Korean leader Kim Jong Un listens during the party congress in Pyongyang. North Korea has brought in more than 100 journalists from around the world to make sure that the 7th Congress of its ruling Workers' Party gets global attention. Four days into the event, they allowed a small number of foreign journalists into the conventional hall where the congress was taking place Workers' Party Congress in North Korea A general view shows the April 25 Palace, the venue of the 7th Workers Party Congress in Pyongyang Getty Images

Mr Jeong declined to give details on the timing of Mr Thae's arrival in the South.

"They are currently under government protection and relevant institutions are going ahead with necessary procedures as usual," he said.

According to the South Korean daily newspaper JoongAng Ilbo, the DPRK Embassy made attempts to figure out the diplomat's whereabouts, but failed.

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The newspaper said Mr Thae's role at the embassy included keeping track of North Korean defectors in and around London and helping to counter the UK's criticism of North Korea's human rights violations.

He also handled consular services.

The Foreign Office said they were not commenting on the reports and could not confirm if they were trying to verify them.

The Government's list of foreign diplomats in the UK shows there are five diplomats in addition to an ambassador based at the DPRK embassy in Ealing, west London.

North Korea often accuses the South of kidnapping or enticing its citizens to defect.

The North has recently resumed its production of plutonium and says it has no plans of stopping nuclear tests as long as perceived US threats remain.

In a written interview with Kyodo, North Korea's Atomic Energy Institute, which has jurisdiction over its main Yongbyon nuclear facilities, said: "We have reprocessed spent nuclear fuel rods removed from a graphite-moderated reactor."

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The institute also said North Korea had been producing highly enriched uranium necessary for nuclear arms and power "as scheduled", Kyodo added.