The political counselor is believed to be the highest-ranking North Korean diplomat to escape to South Korea since 2016.

The diplomat defected in November, the National Intelligence Service (NIS) said.

Details about defections of North Koreans often take months to come to light as the defectors must take courses on South Korean society before they are formally integrated.

South Korean media reports say that the defector was a counsellor responsible for political affairs at the North Korean embassy in Cuba. The NIS has not confirmed this to the BBC.

The Chosun Ilbo newspaper said it was able to interview the diplomat, whom it identified as 52-year-old Ri Il Kyu.

It added that he defected because of "disillusionment with the North Korean regime and a bleak future".

His work reportedly involved stopping Havana from forging official diplomatic ties with Seoul. However, in February, the two governments did establish official relations, in what was seen as a setback for Pyongyang.

"Every North Korean thinks at least once about living in South Korea," the newspaper quoted him as saying.

The last known high-profile defection to the South was that of Tae Yong-ho in 2016. He is North Korea's former deputy ambassador to the United Kingdom.

On Sunday, South Korea marked its very first North Korean Defectors' Day ceremony.

Addressing the ceremony, South Korean President Yoon Suk Yeol promised better financial support for North Korean defectors and tax incentives for companies hiring them.

Mr Yoon, a conservative, has taken a more hawkish approach towards North Korea and on foreign policy general, compared to his predecessor Moon Jae-In.

He supports sanctions against Kim Jong Un's regime and has promised to develop technology to carry out a pre-emptive strike on North Korea if Pyongyang looks to attack Seoul.

The latest defection comes at a time of heightened tensions between the two Koreas.

North Korean leader Kim Jong Un has formally abandoned the goal of reunification with with the South and also recently branded Seoul as "Enemy number One" - a dramatic turnaround from just six years ago when he formally met then South Korean Leader Moon Jae In.

Since then, there has been an upping of rhetoric on both sides of the border.

The two countries floated propaganda balloons along their border towns, with those from the North containing trash and parasites.

And earlier in June, Pyongyang claimed to have test-fired an advanced nuclear warhead missile.