South Korean activists have launched balloons across the border with North Korea carrying thousands of Choco Pies – a favoured chocolate snack that has become the target of a reported crackdown.

About 200 anti-Pyongyang activists released 50 helium balloons carrying 350kg (770lbs) of snacks, including 10,000 Choco Pies, from a park in the border city of Paju, organisers of the event said.

The humble Choco Pie – a confection of chocolate-coated cake and marshmallow – has become an oft-referenced footnote in the volatile history of inter-Korean ties.

Offered as perks to North Koreans working in South Korean factories in the Kaesong joint industrial zone, Choco Pies spawned their own black market and were traded on at sharply inflated prices.

According to media reports in Seoul, the emergence of the South Korean snack as an unofficial currency became too much for the authorities in Pyongyang, who in May ordered the factory owners to stop handing them out.

"Embarrassed by the growing popularity of Choco Pie, North Korea banned it as a symbol of capitalism," said Choo Sun-Hee, one of the organisers of Wednesday's balloon launch.

"We will continue to send Choco Pie by balloons because it is still one of the most popular foodstuffs, especially among hungry North Koreans," Choo told AFP.

South Korean activists regularly launch balloons, usually carrying anti-Pyongyang leaflets, across the border.

Pyongyang has repeatedly pressed Seoul to stop the activists and threatened to shell the launch sites.