SEOUL--One of 260 or so trash balloons from North Korea landed on the roof of a high-rise where the Japanese Embassy is located in Seoul, a diplomatic source said May 30.

Plastic bags of trash and other waste were hung from each of the balloons, which began arriving across South Korea late May 28, military authorities in Seoul said.

The Ministry of National Defense said no human excrement has been discovered in the bags.

Kim Yo Jong, the sister of North Korean leader Kim Jong Un and a senior official of the ruling Workers’ Party of Korea, said in a statement released on the night of May 29 that the balloons were “gifts of sincerity.”

The aerial campaign is seen as a retaliation for 20 balloons carrying leaflets criticizing Kim Jong Un and K-pop videos that defectors in South Korea flew on May 10.

A South Korean foreign ministry spokesman on May 30 criticized the act as “uncivilized and absurd” and called for an immediate halt to a “low-level behavior.”

Local media reported that one of the balloons fell near the foreign ministry building.