North Korean defector Park Sang-hak considers the propaganda balloons he floats into his homeland to be part of a tradition of psychological warfare, and vows to keep going until Kim Jong Un's regime falls.

Park, the son of a North Korean double agent who escaped his country in 1999, has been sending balloons loaded with anti-regime propaganda leaflets, US dollar bills and USB drives of K-pop across the border for nearly 20 years.

His mission is to "enlighten the North Korean public", but the 56-year-old has found himself in the spotlight in recent weeks after Pyongyang singled him out as "scum" and sent more than 1,000 balloons carrying trash into South Korea in retaliation.

Another wave of trash-bearing balloons forced a three-hour halt to flights in and out of Seoul's Incheon airport early Wednesday morning.

This is an "unacceptable" subversion of the rules of the game, Park told AFP, adding that never in the decades of leaflet warfare between the two Koreas has either side sent garbage across the border.

"Kim Jong Un stands out as the first person ordering balloons of trash," he said, calling it a "despicable and atrocious act" and demanding Kim apologise.

Park has first-hand experience of the power of a propaganda leaflet.

He vividly remembers a leaflet he found decades ago in the North, which purported to show two successful defectors in the South.

"One picture shows this defector with pretty South Korean women in swimming suits, with the text saying he had received 100 million won in government aid," Park said.

It changed Park's life, showing him that defection was not only for elite diplomats or border soldiers, but was possible for anyone who dared to cross the river into China.

'Important information'

"It was the most important information for me," he told AFP. 

A few years later, he, his mother and two siblings crossed the river themselves.

The leaflet seen by Park was made by the South Korean government. He later met one of the defectors in the photograph and asked him whether it was real.

"He told me it was staged by Seoul's National Intelligence Service," Park said.

Both Seoul and Pyongyang used to produce their own propaganda leaflets and run loudspeaker broadcasts near the border. South Korea produced radio shows specifically to be beamed into the North.

But the two countries called off their duelling campaigns in 2003, during a period of warmer ties, which prompted Park to decide to start his own activities.

Park sent his first balloon northwards in 2006. 

At first, he used balloons bought from a toy shop, but through a process of trial and error he improved his method.

Now he says he can send fully packed balloons -- each weighing seven or eight kilograms (15 or 18 pounds) -- "with my eyes closed", although for operational security reasons, he declined to reveal details of his launches.

The balloons hold special waterproof leaflets which are designed to safely carry a single dollar bill, a key part of his campaign's success, Park says.

North Koreans learn there are dollar bills dropping from the sky, he said, prompting them to find and open the balloons' packages when they see them. And that leads them to read the leaflets.

One missive -- all are written by Park and his staff -- details the killing of Kim Jong Un's half-brother Kim Jong Nam in Kuala Lumpur International Airport in 2017, including a photo of his slumping body.

'Deliver truth'

Pyongyang's reaction to his balloons proves they have an impact on the North Korean public, Park said.

It is hard to imagine how little information the North's 26 million people have access to, Park said, with the internet and media controlled by the regime.

This is why the leaflets matter and why they work, he said.

"I have received calls from around 800 defectors thanking me for my mission, telling me that they had seen my leaflets in the North," he said, adding that he wouldn't stop his campaign.

His critics claim his actions risk escalating the tense security situation between the two Koreas, which remain technically at war since the 1950 to 1953 conflict ended with an armistice, not a peace treaty.

But Park dismisses the accusations, saying his campaign is peaceful: "While Kim is firing missiles non-stop, our message is to stop such violence."

His ultimate aim is for the Kim regime to fall, which he hopes can happen due to domestic change, not an outside intervention.

"These leaflets will deliver truth to the North Korean people, who will then use them to rise up against the Kim regime and topple it," he said.

"My leaflets are of truth, money and love."