Seoul warned the public on Saturday to avoid more balloons sent from North Korea and to report them to the military or police.
South Korea's military said North Korea was sending more balloons carrying "filth" across the heavily fortified border.
North Korea sent hundreds of balloons carrying trash and excrement earlier this week, calling them "gifts of sincerity" and vowing to send more. On Saturday, South Korean Defence Minister Shin Won-sik called this "unimaginably petty and low-grade behaviour".
A public message broadcasted by the city of Seoul asked the public to refrain from touching balloons "identified in the sky near Seoul" and report them as they were "being handled by the military".
Other regional governments had been asked to broadcast similar messages, the defence ministry said.
North Korea has said the balloons were retaliation for an ongoing propaganda campaign by North Korean defectors and activists in South Korea, who send balloons containing anti-Pyongyang leaflets, food, medicine, money and USB sticks loaded with K-pop music videos and dramas across the border.
Ukraine issued air raid alerts for Kyiv and the country's eastern half as blasts shook the city of Mykolaiv early on Monday, authorities said, hours after the one-day Easter ceasefire declared by Russian President Vladimir Putin came to an end.
US Vice President JD Vance began a four-day visit to India on Monday and will hold talks with Prime Minister Narendra Modi, as New Delhi rushes to avoid steep US tariffs with an early trade deal and boost ties with the Trump administration.
The Israeli military on Sunday said a review into last month's killing of emergency responders in Gaza found there had been "several professional failures" and that a commander would be dismissed over the incident.
US President Donald Trump is threatening to cut another $1 billion in funding for Harvard University, this time targeting health research, the Wall Street Journal reported on Sunday, as the administration's row with elite schools escalated.