South Korea has fired into North Korea after an "unidentified object" was sent towards the country.
South Korea's Joint Chiefs of Staff said in a statement that the South Korean military bolstered its air surveillance and broadcast a warning to North Korea in response to the object. It provided no other details.
The mystery flying object may have been a drone, local media speculated.
South Korea's Yonhap news agency, without citing a source, reported that South Korea fired about 90 machine gun rounds into the air and toward North Korea. It said South Korea was analyzing whether a North Korean drone had crossed the border.
The Koreas face off across the world's most heavily armed border, and the two sides occasionally clash. In 2014, they traded machine gun and rifle fire after South Korean activists released anti-North Korean propaganda balloons across the Demilitarized Zone that bisects the Korean Peninsula, but no casualties were reported.
Attacks blamed on North Korea in 2010 killed 50 South Koreans.
Additional reporting by Associated Press
