(ATTN: UPDATES with one more artillery round fired by North Korea)
SEOUL, Aug. 10 (Yonhap) -- North Korea fired one more artillery round into waters near a disputed inter-Korean maritime border Wednesday, prompting South Korea to fire back in retaliation, military officials said.
Residents on Yeonpyeong island near the Yellow Sea border reported hearing the firing of three artillery shells from a North Korean shore battery Wednesday evening. However, South Korea's military said only one round landed in waters near the border.
It was the second artillery shells fired by North Korea Wednesday into the Northern Limit Line (NLL) that serves as a de facto border in the area. Earlier in the day, the North fired three artillery rounds, provoking South Korea to counter with the same number of shells.
"An artillery round believed to be from a North Korean shore battery landed in waters near the border at about 7:46 p.m., to which our side fired three warning shots," South Korea's Joint Chiefs of Staff said in a brief news statement.
"Our forces in the area are keeping a close watch on North Korean movements," it said.
Tension remains high along the poorly defined border, the scene of a series of bloody naval clashes between the two Koreas. North Korea has never recognized the NLL, demanding that it be re-drawn further south.
Earlier, the JCS said the South's Navy heard North Korea fire three artillery shots toward the NLL around 1 p.m. Wednesday, and then responded around 2 p.m. with three warning shots.
"We estimated that one North Korean shell dropped near the NLL," a JCS official said. "We haven't noticed any particular movements in the North Korean military but we're maintaining a defense posture."
The official said the North Korean shots appeared to have come from Yongmae Island, about 11 kilometers north of the NLL and some 20km northeast of Yeonpyeong Island. The South's warnings shots were launched from Yeonpyeong, the official said.
The official explained that the South took its time to assess the situation before firing warning shots.
"If we had sustained any damage or if the shots had landed near our vessel, then we would've responded immediately," the official said. "But the shot appeared to have fallen near the NLL, and we directed our warning shots toward the line."
Another JCS official said it was difficult to determine whether the North Korean shell had actually crossed the NLL because of the lack of visibility in the Yellow Sea.
Last November, North Korea shelled Yeonpyeong Island, killing two civilians and two Marines. It was the North's first attack aimed at South Korean territory since the end of the 1950-53 Korean War, and its second deadly provocation against the South in 2010. In March, the North torpedoed the South Korean warship Cheonan in the Yellow Sea, killing 46 sailors aboard.
The NLL, which U.N. forces drew unilaterally at the end of the Korean War, has served as the de facto maritime boundary between the two Koreas. They still remain technically in a state of war since the Korean War ended with an armistice, not a peace treaty.
The North has contested the legitimacy of the NLL in recent decades and has demanded that it be redrawn, a request that the South has rejected.
The two Koreas have engaged in three bloody naval skirmishes in waters near Yeonpyeong, most recently in 2009.
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