A North Korean patrol boat sailed about 2.8 kilometers into the South-controlled waters last night but quickly retreated after a South Korean broadcast warning, according to Seoul's Joint Chiefs of Staff.
In less than an hour, another North Korean patrol boat intruded across the border but returned to its waters after another warning broadcast and two shots from the South Korean vessel, a Joint Chiefs of Staff officer said on condition of anonymity citing department policy. There were no injuries reported, he added.
The Korean maritime border is not clearly marked, and violations by North Korean military and fishing boats are not unusual. But yesterday's incursion marks the North's first border violation since the 1,200-ton South Korean warship went down near the area on March 26, killing 46 South Korean sailors.
Seoul has not directly blamed North Korea for the sinking, and Pyongyang has denied involvement, but suspicion has focused on the North given its history of attacks.
The two Koreas remain technically locked in a state of war because their three-year conflict ended in a truce, not a peace treaty, in 1953. Their navies fought three bloody sea battles near the disputed sea border since 1999.
South Korea has said it will take stern action against anyone responsible for the sinking - one of its worst maritime disasters.The government was to announce the results of its investigation in the coming week.
Today, Yonhap news agency reported that South Korean investigators have obtained unspecified evidence showing North Korea's involvement in the sinking.
Yonhap cited an unidentified government source as saying South Korea's military was considering issuing an anti-North Korea statement after the investigation outcome is announced.
South Korea's Defense Ministry and Joint Chiefs of Staff said they could not confirm the report because the investigation was still under way.Meanwhile, the foreign ministers of South Korea, China and Japan met at the southeastern Korean city of Gyeongju over the weekend ahead of a three-country summit set for later this month.
During the meeting, Japan promised to closely cooperate with South Korea over its handling of the ship sinking, while China stressed the investigation must be scientific and objective, Yonhap reported.