Black Venus -- the South Korean spy who met Kim Jong Il

In the 1990s he posed as a disgruntled former South Korean military officer turned businessman looking to film commercials for Southern companies in scenic Northern locations.

Along the way to meeting Kim, he claims to have sold antique ceramics for millions for members of the North's ruling family, and seen Northern military officials counting huge bribes paid by Southerners in political plots.

Now his story has been turned into a book and a film that shine new light on the murky connections -- some financial, some political -- that run across the Demilitarised Zone dividing the peninsula.

With North and South engaged in a rapid diplomatic rapprochement, "The Spy Gone North" has been an instant bestseller and box office hit, the film attracting five million viewers in just its first three weeks on release -- around 10 percent of the South's entire population.

"It was extremely stressful living as a spy," Park, 64, told AFP in a rare foreign media interview. "I might be exposed by the slightest mistake, like a stupid slip of the tongue."

But unlike Northern agents sent south, he was not issued with suicide pills to ensure a quick end if captured.

Instead, he explained, "we were trained to kill ourselves with our own fingers" using "some critical points in the body".

- Fake Rolex -

Park started in military intelligence in 1990, tasked with gathering information on the North's nuclear programme, then in its early stages.

He befriended a Chinese nuclear physicist of Korean ancestry who -- in exchange for a million-dollar payment -- later revealed that the North had made two low-level nuclear weapons.

When he joined the South's spy agency in 1995, then known as the Agency for National Security Planning (ANSP), he was assigned the codename Black Venus.

Based in Beijing, he worked for a South Korean company importing Chinese agricultural products, disguising them as tariff-exempt North Korean goods, and built up a network of North Korean contacts and other informants.

He also bribed his way towards higher North Korean authorities, once providing the acting head of Pyongyang's spy agency with top-quality counterfeit Rolex watches when he visited Beijing.

His big break came, he says, when he allegedly helped arrange the release of a nephew of Jang Song Thaek -- the influential uncle of current leader Kim Jong Un who was executed as a traitor in 2013 -- from a Chinese prison by helping pay off $160,000 of debts the nephew owed to Chinese traders.

A grateful Jang family invited Park to Pyongyang and he seized the chance to sign a $4 million deal between his advertising company and a North Korean tourism agency to film TV commercials at locations including Korea's spiritual home, Mount Paektu, and Mount Kumgang, where the two sides hold reunions of divided families.

At the time North Korea was in desperate need of funds, with its socialist economy falling apart following the collapse of the Soviet Union, its main funder, and millions of its people starving.

Park says he helped members of the Kim family sell antique pale green glazed celadon ceramics unearthed in the North to rich South Koreans, and visited a cache of hundreds more hidden near Mount Myohyang, accompanied by a South Korean expert who valued them at more than one billion dollars.

In 1997, after several trips to the North, he was taken to the Paekhwawon Guest House in Pyongyang, where Kim Jong Il was as usual working by night, for a 30-minute meeting with the leader himself, the recorder hidden in his urethra.

Kim did not bother to shake hands when he entered the room for the 30-minute meeting, Park said, which focused on cashing in the ceramics.

"His voice was a bit husky," said Park. "Far from being nervous for fear of being exposed, I felt rather relieved because it meant I had won the North's complete trust."

- North Wind -

Kim also expressed a keen interest in the South's upcoming presidential poll, according to Park.

Cross-border military crises have tended to occur in election years in the South, helping shift undecided votes toward conservatives, a phenomenon known as "the North Wind" in the South.

North Korean agents blew up Korean Air flight 858 over the Andaman Sea, killing 115 people, less than three weeks before the South's 1987 presidential election.

And ahead of the 1997 presidential poll, Park says, North Korean officials told him three supporters of conservative candidate Lee Hoi-chang had asked them to mount an armed attack days before polling.

In a Beijing hotel room, Park claims, "with my own eyes, I saw the North Koreans counting wads of dollars in their hotel room that they received from the South Koreans", allegedly in exchange.

"There were 36 bundles, each of them $100,000."

He reported his findings to his ANSP bosses and the campaign of liberal candidate Kim Dae-jung, which made them public. In the end there was no incident and Kim secured a narrow victory.

The trio of Lee supporters were later convicted of breaking the South's National Security Law, which bans contact with the North, but were acquitted on appeal to the Supreme Court after Park refused to testify.

- Final exposure -

His cover blown, Park was fired by the spy agency and moved to China, spending much of his time on the golf course.

The ANSP, now known as the National Intelligence Service, declined to comment on Park's allegations.

After South Korea's conservatives returned to power, they brought in a new spy chief and Park was arrested in Seoul in 2010 and convicted of passing classified information to the North, despite insisting he conveyed only low-level intelligence to win Pyongyang's confidence.

"I was in solitary confinement for six years," he said, calling his imprisonment politically motivated.

His story provides a glimpse into a "suspected but so far inaccessible truth" in inter-Korean relations, film critic Lee Yong-cheol wrote in Cine21 magazine.

And if the winds of geopolitics once again shift and leave him on the wrong side, Park has an insurance policy -- the recordings he made of his meetings with Kim Jong Il, Jang Song Thaek and other officials.

He says they were not available when he was suddenly arrested in 2010.

But now he is keeping them safe "somewhere in a foreign country".