North Korean leader Kim Jong-Un has a secret son who is heir to his brutal regime, spies have revealed.

The dictator has three children with his wife Ri Sol-ju but the gender of the couple's first - who was born in 2010 - has never been revealed.

Following the birth of their son the couple had a baby girl in 2013 and another child just six months ago, according to previous reports from South Korea's intelligence agency.

The first lady had disappeared for an extended period last year, raising speculation that she could be pregnant.

This photo of Kim Jong-Un and his wife Ri Sol-ju, was taken in March, just weeks after she is said to have given birth to the couple's third child

Proud parents? North Korean leader Kim Jong-Un and his wife Ri Sol-Ju had their third child in February this year

According to previous intelligence reports from Seoul's spy agency, Ri married Kim in 2009 and gave birth to their first child the following year, with their second born in 2013.

Kim is the third generation of his dynasty to rule North Korea, but little has been revealed about the country's first family.

Former NBA star Dennis Rodman, following his trip to the nation in 2013, has been the only source of information about the couple's young daughter - a baby girl named Ju-Ae.

Saying that he had held Kim's daughter in his arms, Rodman described the North Korean leader as 'a good dad' who has 'a good family'.

While more of a public personality than his introverted father Kim Jong-Il ever was, Kim's own personal details remain little known. He is pictured with his wife Ri Sol-ju

Intelligence reports have described Ri, pictured right, as coming from an ordinary family, with her father an academic and her mother a doctor

While more of a public personality than his introverted father Kim Jong-Il ever was, Kim's own personal details remain little known.

Even his exact birthday and the date of his wedding have not been confirmed.

Intelligence reports have described Ri as coming from an ordinary family, with her father an academic and her mother a doctor.

She visited South Korea in 2005 as a cheerleader for her country's squad in the Asian Athletics Championships.

The secret son has been revealed after North Korea today detonated a hydrogen bomb sparking a powerful 6.3 magnitude earthquake amid an 'escalating' nuclear crisis.

Former NBA star Dennis Rodman, pictured far right, following his trip to the nation in 2013, has been the only source of information about the couple's baby daughter

The terrifying tremor was detected in the northeast of the country where the Punggye-ri test site is located - but was so strong that it shook buildings in China and Russia.

State television claimed the country's sixth nuclear test - 10 times more powerful than its fifth - was a 'perfect success' and could pave the way for a frightening new range of missiles loaded with hydrogen bombs.

It added that the underground test - which was directly ordered by leader Kim Jong-un - was a 'meaningful' step in completing the country's nuclear weapons programme.

The recent development comes amid heightened tensions following Pyongyang's test launch of two missiles in July that potentially could hit major mainland US cities.

The regime frequently flaunts its intercontinental ballistic missile technology and has repeatedly tested hydrogen bombs - but has so far been unable to combine the two into a lethal weapon.

However, Jong-un claims the latest explosive - which seismologists calculated to be eight times as damaging as the Hiroshima nuclear bomb dropped by the US in World War II - could be packed into a warhead and fired towards US territory.