A North Korean warship was heavily damaged Tuesday when the navies of the two Koreas briefly exchanged fire, South Korean military officials said.
South Korean Commodore Lee Ki-sik said the shooting lasted for about two minutes, adding that a South Korean ship was lightly damaged.
"It's a regrettable incident," Lee told reporters in Seoul. "We are sternly protesting to North Korea and urging it to prevent the recurrence of similar incidents."
The North Korean military blamed South Korea for the clash, claiming that South Korean ships had crossed into its territorial waters. The official Korean Central News Agency reported that North Korea demanded an apology.
In a statement, the South Korean joint chiefs of staff said North Korean patrol boats crossed a disputed western sea border around 11:27 a.m. local time. A South Korean ship responded with a warning shot. A North Korean ship opened fire, but turned back in flames after being hit by return fire from South Korean ships, the statement said.
Travelling with U.S. President Barack Obama on Air Force One, White House spokesman Robert Gibbs told reporters the administration was aware of the clash and urged restraint on the part of North Korea.
"I would say to the North Koreans that we hope that there will be no further actions in the Yellow Sea that can be seen as an escalation," Gibbs said, referring to the body of water where the shooting took place, which Koreans in both the North and South call the West Sea.
UN spokesman Farhan Haq said UN Secretary General Ban Ki-moon is watching the situation and has called for "maximum restraint" by both parties.
1 killed, 3 wounded: source
South Korean broadcaster YTN television said one North Korean officer was killed and three other sailors wounded, citing an unidentified government source. The report was not confirmed by the South Korean Joint Chiefs of Staff.
The incident took place about 220 kilometres off the South Korean port city of Incheon, near the island of Daecheong, which is controlled by South Korea.
The skirmish took place as U.S. officials said President Barack Obama had decided to send a special envoy to North Korea for talks on that country's controversial nuclear program.
It was an intentional provocation by North Korea to draw attention ahead of Obama's trip," said Shin Yul, a political science professor at Seoul's Myongji University.
The sea border between the Koreas is a source of tension, as the two sides have yet to agree on it more than 50 years after the Korean War. The current border was drawn out unilaterally by the then United Nations commander.
Last month, North Korea accused South Korean ships of entering its territorial waters on the west coast.
The two sides have had deadly encounters over the years. In 2002, six sailors from South Korea died in a skirmish. It is unclear how many North Korean casualties have occurred.