South Korea's navy has fired warning shots at North Korean fishing boats after they crossed into the South's territory. A series of such incursions is raising tensions on the Korean Peninsula.
South Korea's Defense Ministry says three North Korean boats retreated after the navy fired warning shots early Sunday. A spokesman says the shots were fired into the sky and there are no reports of injuries or damage.
There have been six encounters between boats from North and South Korea along the disputed western maritime border in the past week. Seoul has protested to Pyongyang about the incursions.
North Korea accuses South Korean warships of crossing the boundary and warns that further such moves could lead to serious consequences. The South denies crossing into the North's territory.
The incursions come at a time of heightened tensions on the peninsula. North Korea has reacted angrily to demands from South Korea, the United States and other countries that it give up its illegal nuclear weapons programs. In the past few weeks, Pyongyang has warned that South Korea would face "disaster" if it continues to align itself with Washington on the issue.
A military spokesman in Seoul says South Korea is studying whether the recent incursions in the Yellow Sea are deliberate.
The sea border between the two Koreas is not clearly marked and North Korea claims the boundary is farther south than the internationally recognized demarcation line. The latest incidents come during the lucrative season for catching crabs, which the impoverished North may need to feed its people or for trade.
Encounters in the disputed waters have turned violent in recent years. A skirmish four years ago killed an estimated 30 North Koreans. A similar encounter a year ago left six South Korean soldiers dead. South Korean President Roh Moo-Hyun has warned that special care is needed to avoid another sea battle.
Sunday's incident took place as U.S. Deputy Secretary of Defense Paul Wolfowitz arrived in South Korea to discuss the North Korea situation.
On Monday, he is to meet with President Roh and Foreign Minister Yoon Young-kwan. Tensions have been high on the Korean peninsula for seven months. Last October, the United States said Pyongyang had revealed it was pursuing a clandestine nuclear weapons program in violation of international accords.