Propaganda leaflets from a trash-carrying balloon lie scattered on the ground of alleys near the presidential office in Yongsan-gu, Seoul on Thursday. (Son Ji-hyoung/The Korea Herald)

North Korea on Thursday flew another batch of trash balloons toward the South, most of which landed in Seoul and nearby areas, including Yongsan where the presidential office is located, according to the South Korean Joint Chiefs of Staff.

For the first time since the balloon offensive began in May, the balloons carried leaflets targeting President Yoon Suk Yeol and his wife, Kim Keon Hee. Some leaflets called Yoon a “thug” while others accused the first lady of going on extravagant overseas trips and wearing expensive jewelry.

Some of the North Korean leaflets fell at the presidential office compound in Yongsan, according to the Presidential Security Service. The balloons did not contain dangerous items, it added.

While North Korean leader Kim Jong-un’s sister Kim Yo-jong has blamed “political propaganda trash” leaflets flown by South Korean activists for their balloon releases, the National Intelligence Service in Seoul has said the two are not correlated.

According to a new NIS analysis obtained by The Korea Herald, the South Korean intelligence agency said North Korea sending balloons loaded with trash across the border was not due to leafleting by South Korean activists, as Pyongyang has claimed.

“Leaflet activism by some civic groups does not appear to be linked to North Korean filth balloon releases,” the intelligence analysis said. “North Korea appears to be floating the balloons on an arbitrary schedule, with no discernible pattern.”

The NIS thinks North Korea is likely to ramp up launches of the balloons in the months to come.

“Since September, North Korean provocations using filth balloons have increased dramatically,” it said. About two-thirds of North Korea’s balloon launches over the year have taken place since the beginning of September.

“In light of North Korea recently intensifying its offensive against the South, it is anticipated that balloon provocations would not only continue, but increase to get Seoul to change its policies toward Pyongyang and to make a statement as the US presidential election unfolds,” it said.

The intelligence agency noted that North Korea was also likely to utilize the northerly wind blowing to the south during winter.

On concerns that North Korea could weaponize the balloons to conduct bioterrorism, the NIS said the likelihood was low.

“It is unlikely North Korea would use the balloons to spread infections or other harmful agents especially given large numbers of them have invariably landed within their own territory,” it said.

Balloons are difficult to control or maneuver, making them “ineffective as a means for releasing harmful biological agents,” it said. While some balloons have been equipped with timers and GPS receivers, other details of the technical capabilities of North Korean equipment attached to the balloons were still being analyzed.

To date, no substance of public health concern has been found in the content of the balloons. While some parasites were detected in compost contained in the balloons released in May and June, as they were collected immediately by the military, no contamination occurred.

As using the balloons for such a biological attack would mean actively initiating war, North Korea would want to avoid the risk considering retaliation from the South Korean government and international condemnation, it said.

“The NIS is keeping all possibilities open, including North Korea possibly using balloons for biological terrorism, and continues to work closely with the concerned government agencies,” it added.

The NIS saw that the chief aim of North Korea in continuing to deploy filth balloons was to instill insecurity within South Korea and stir division.