The Joint Chiefs of Staff reported that North Korea began releasing the balloons around 9 a.m.
"We will respond resolutely and calmly according to our response manual, with the utmost priority on public safety," the JCS said.
It marks the 17th such incident since May 28, when the North began the launches in retaliation for anti-Pyongyang leaflets sent across the border by defectors and activists in South Korea.
On Saturday evening, about 200 balloons were floated, with about 50 debris items discovered in northern Seoul and Gyeonggi Province.
The balloons contained paper, vinyl bags and plastic bottles. Military officials said no hazardous materials were found.
The military warned citizens to exercise caution and report any fallen objects to nearby military units or police without touching them.
The balloon launches have caused significant property damage in the greater Seoul area.
Yang Bu-nam, a Democratic Party lawmaker, reported Sunday that from May 28 to Aug. 10, damages totaled over 100 million won ($74,700), based on data from Seoul and Gyeonggi Province.
