North Korea said a ship sunk by South Korean naval vessels was a peaceful fishing boat that the South Koreans had tried to capture. South Korean defense officials said the unidentified boat was sunk after it opened fire. The incident, in which North Korea said a fisherman was killed, took place near the demilitarized zone separating north and south. Naval battles between the two occurred as recently as last fall. The latest negotiation attempt was suspended by the north early this year to protest joint U.S.-South Korean military exercises.