N Korea shells fall near South line
South Korean forces have returned fire after North Korean artillery shells fell into waters near the tense maritime line which separates the two rivals, a South Korean defence official said.
North Korea fired three shells near the Northern Limit Line in the Yellow Sea, prompting the South to fire three shells back, defence ministry spokesman Kim Min-seok said.
South Korean forces have been on high alert in the area since a North Korean artillery attack killed four people on South Korea's Yeonpyeong island in November.
Wednesday's shelling was near that island.
Violence often erupts in the contested waters. Boats routinely jostle for position during the crab-catching season, and three deadly naval clashes since 1999 have cost a few dozen lives.
Mr Kim said one North Korean artillery shell is believed to have fallen south of the maritime line, citing a preliminary analysis of the trajectory of the shell.
The line separating the countries was drawn at the close of the Korean War but is still a fierce point of dispute.
North Korea argues that the line should run further south. Seoul believes that accepting such a line would endanger fishing around five South Korean islands and hamper access to its port at Incheon.
The November attack marked a new level of hostility along the contested line. Two civilians and two marines died, and many houses were gutted in the shelling.
The countries remain technically at war after the 1950-53 Korean War.