North Korea is accusing the South Korean military of firing on North Korean troops guarding the tense land border that separates the two countries.
North Korea's state-run news agency says South Korean forces committed what it calls a "grave armed provocation" Sunday. It says they fired toward a North Korean police post in the eastern part of the demilitarized zone. South Korea's military says no such incident took place.
Pyongyang regularly accuses Seoul of raising tensions between the two states, which remain technically at war since a 1953 truce that ended the Korean War.
South Korea also is investigating whether North Korea played a role in the mysterious sinking of a South Korean warship near their disputed western sea border on March 26. The incident left 45 sailors missing and feared dead. Pyongyang has remained silent about the sinking.
South Korea's military began salvage operations on the warship Sunday after calling off rescue efforts at the request of relatives of the missing. Military officials say work to recover the 1,200-ton Cheonan may take weeks.
Some information for this report was provided by AP, AFP and Reuters.