North Korea fired at least one artillery shot which landed near a South Korean navy patrol ship south of the two sides' disputed sea border today.
However, it did not hit the vessel, a military official in Seoul said.
YTN news channel reported that South Korean artillery fired at a North Korean naval vessel in response.
Residents of the Yeonpyeong island, which lies just south of the disputed sea border and which was shelled by North Korean artillery in 2010 killing four people, have evacuated to bomb shelters.
There was no further firing from the North following the incident, soon after 6pm local time (0900 GMT), the official said.