According to South Korean information, North Korea has flown several drones over the inner-Korean border, prompting South Korea to fire warning shots.
The first "North Korean unmanned aerial vehicle" has been spotted around Gimpo airspace in Gyeonggi province, the South Korean general staff said on Monday.
Overall, several drones entered South Korea's airspace in the border regions around Gyeonggi Province.
Seoul then fired warning shots and deployed fighter jets and helicopter gunships.
According to the South Korean news agency Yonhap, South Korean warplanes tried to shoot down the North Korean drones.
The military in Seoul initially did not comment on whether drones were shot down or whether they flew back over the border.
According to Yonhap, one of the North Korean warplanes crashed into South Korea's Hoengseong district.
As Yonhap also reported, citing an official from the South Korean Minister of Transport, air traffic at Gimpo and Incheon International Airports was suspended for about an hour at the request of the General Staff.
It is the first time in five years that North Korean drones have entered South Korean airspace.
The internationally isolated country has already tested numerous weapons this year.
According to Seoul, Pyongyang fired two rockets last Friday.