ANKARA

North Korea once again resumed sending balloons believed to be filled with waste across the border, raising tensions with the South, Seoul said on Saturday.

South Korea's Joint Chiefs of Staff said the balloons were suspected to be carrying waste materials and may drift toward the northern part of Gyeonggi province surrounding the capital Seoul, Yonhap News reported.

The public has been urged to avoid contact with the balloons and report any sightings to local authorities, according to the South Korean news agency.

The issue of balloon exchanges between the Koreas has a contentious history. In the past, North Korean defectors and activists based in South Korea have launched large balloons carrying anti-Pyongyang propaganda leaflets across the border.

These actions have often been met with sharp criticism from the North.

In response to these leaflet campaigns, North Korea began sending waste-filled balloons into South Korea in late May.

The North's actions, which they have described as an exercise of "freedom of expression," have been condemned by South Korea as provocative and hazardous.