North Korea floated around 310 balloons carrying trash south across the border overnight, the Yonhap news agency reported citing Seoul's military, after Kim Jong Un's powerful sister warned of a "new counteraction".

"The latest batch of waste-loaded balloons sent late Sunday contained scrap paper and plastic, with no toxic material detected so far," Yonhap said, citing the Joint Chiefs of Staff. It added that no additional balloons were detected floating in the air as of early Monday.