Rubbish being carried by balloons from North Korea has been dumped on the South Korean presidential compound.
Hundreds of balloons were launched from North Korea, with one hitting the South Korean leader's office, which is a designated no-fly zone, for the first time.
The two nations have been locked in a tit-for-tat Cold War-style campaign with South Korea ramping up its broadcasts of K-pop songs and propaganda messages across the rivals’ heavily armed border.
North Korea floated balloons filled with rubbish over the border throughout June as escalating tensions highlighted the fragile state of inter-Korean relations.
The items dropped on the presidential office contained no dangerous material and no one was hurt, South Korea's presidential security service said.
Experts have said South Korea should shoot down incoming North Korean balloons to protect key facilities as they might contain dangerous substances in future campaigns.
Seoul officials earlier said North Korea had used the direction of winds to fly balloons toward South Korea, but some of the past balloons had timers that were likely meant to pop the bags of trash midair.
The security service gave no further details about the rubbish found at the presidential compound.
It refused to disclose whether President Yoon Suk Yeol was at the compound when North Korean balloons were flying over his office.
If North Korea is found to have used timers or any other device to deliberately dump trash on the presidential office, it would certainly invite a strong response by South Korea.
But experts say dropping balloons on ground targets requires advanced technology and that North Korea would certainly lack such an ability.
"Some of (the hundreds of balloons) launched by North Korea landed on the presidential compound by coincidence. North Korea has no technology to precisely drop balloons at certain targets," said Jung Chang Wook, head of the Korea Defense Study Forum think tank in Seoul.
He said North Korea likely wanted the balloons to fall on Seoul, about an hour's drive from the border, after calculating factors like the weight of the trash bags tied to the balloons, the volume of air in the balloons and the weather conditions.
Lee Illwoo, an expert with the Korea Defense Network in South Korea, said that strong winds in Seoul would also make it impossible for North Korea to target certain places with balloons.
South Korea's Joint Chiefs of Staff said earlier on Wednesday that North Korea had restarted floating balloons across the border, the 10th such launch since late May.
More than 2,000 North Korean balloons have been discovered in South Korea in the past weeks carrying wastepaper, scraps of cloth, cigarette butts and even manure.
North Korea has said it was responding to South Korean activists scattering political leaflets across the border via their own balloons.
The North's balloons haven't caused major damage but have raised security jitters among people worried North Korea could use such balloons to drop chemical and biological agents.
South Korea has avoided shooting at balloons citing concerns about damages and the possibility they might contain hazardous substances.
South Korea said on Sunday it was ramping up its anti-Pyongyang propaganda broadcasts from its loudspeakers at all major sites along the land border because North Korea was continuing launches of trash-carrying balloons.
It restarted its loudspeaker broadcasts for the first time in about 40 days last week in retaliation for North Korea's previous balloon activities.
