SEOUL North Korea declared a no-sail warning on Monday for areas off its west coast near a disputed border with South Korea and has notified the South that it will conduct firing drills, a South Korean government official said.
The area is near the so-called Northern Limit Line, drawn up at the end of the 1950-53 Korean War, which the North has refused to recognize. Past clashes between the two navies in the area killed scores of sailors on both sides.
The warning comes amid heightened tensions surrounding the North after the U.N. Security Council condemned Pyongyang for its mid-range missile launches last week, just as the leaders of South Korea, Japan and the United States met to discuss the North's arms program.
The areas marked by the North are north of the naval border but lie close to islands populated by civilians, said the official, who requested anonymity. South Korea's military will be watching closely for any infringement of its waters, he said.
The standoff marks the latest incident in a long line of conflict arising from the a sea border bitterly contested by the rivals in one of the world's most heavily armed regions, with about 1.8 million soldiers.
"It's up to the two militaries either to recognize or reject their own claimed line, and challenge the other's - this goes back and forth, so this is probably another episode of that," said Daniel Pinkston of the International Crisis Group.
At the weekend, North Korea accused the South of "gangster-like" behavior by "abducting" one of its fishing boat and threatened to retaliate.
South Korea returned the boat, which had drifted across the maritime border, and its three crew members on Friday and said the vessel had experienced engine failure.
A South Korean navy ship was sunk in 2010 by what Seoul said was a torpedo attack by the North that killed 46 sailors, an attack that led to the suspension of most exchanges across the border. Pyongyang denies any role and calls the accusation "a farce".
The North bombed one of the islands near the border later that year, killing four people.
(Reporting by Jack Kim and James Pearson; Editing by Paul Tait)