Trash from at least one North Korean balloon fell on the South Korean presidential compound on Wednesday, raising worries about the security of key South Korean facilities from North Korean provocations.

It was the first time the South Korean leader's office in downtown Seoul, which is protected by scores of soldiers and a no-fly zone, had been directly hit by any of the thousands of trash-carrying balloons launched by Pyongyang since May.

"The chemical, biological and radiological (warfare) response team has safely collected the trash balloons," the presidential security service told reporters.

"After investigation, results have confirmed that there were no danger or contamination of the object," it said.

But experts said South Korea needs to shoot incoming North Korean balloons at border areas next time, as it was not clear whether North Korea would put in hazardous items in future campaigns.

North Korea's latest balloon launches came days after South Korea boosted its frontline broadcasts of K-pop songs and propaganda messages across the rivals’ heavily armed border.

Their tit-for-tat Cold War-style campaigns are inflaming tensions, with the rivals threatening stronger steps and warning of grave consequences.

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, like whether balloons were discovered along with the trash. (Agencies)