A survey shows trash-carrying balloons Pyongyang has recently flown into South Korea have landed at over 770 locations across the country.
North Korea has repeatedly flown such balloons toward South Korea since May 28, to retaliate for balloons with anti-Pyongyang leaflets sent to the North by North Korean defectors in the South.
A document disclosed by the South Korean National Police Agency to a South Korean lawmaker showed more than 1,600 such balloons are estimated to have been flown by the North and their landings were confirmed at 778 sites.
The locations cover a vast area, including the capital Seoul, the eastern province of Gangwon and the southeastern city of Gyeongju.
An expert is expressing concern that balloons could be used in possible biological or chemical weapon attacks.
In opinion poll released on Friday, 60 percent of people surveyed said they saw North Korean balloons as a threat, while 36 percent said they did not.
On Sunday, the South Korean military responded by conducting anti-Pyongyang propaganda loudspeaker broadcasts near the military demarcation line for the first time in six years. The military said whether it will continue the broadcasts or not is up to Pyongyang.
The South Korean military is on alert for further possible balloons coming from North Korea.