South Korea's navy ships are anchored near the Yeonpyeong Island, South Korea, Thursday, Nov. 24, 2011.
In an incident sure to raise tensions in the region, North Korea fired at least one shot into disputed waters toward a South Korean naval ship, a South Korean military official said Thursday.
The artillery did not hit the vessel, and South Korea fired back at the North Korean naval ship in response, Reuters reports. The exchange occurred in the Yellow Sea just north of Yeonpyeong Island, where residents were ordered into bomb shelters. Yeonpyeong, which is approximately seven miles off North Korea's coast, is near a disputed maritime demarcation border called the Northern Limit Line.
Though the group of five islands technically belong to South Korea, as per a United Nations agreement made in 1953, North Korea started pushing back in the 1990s and has since frequently fired artillery across the line. Four South Koreans were killed on the island by North Korean artillery in 2010.
Earlier this week, the South Korean Navy fired 10 warning shots at three North Korea ships after they crossed the so-called Northern Limit Line around 4 p.m. local time. The North Korean ships retreated back to their side of the line.
Earlier on Thursday, North Korea had issued a threat to "blow up" any South Korean military ships, calling South Korea's move "a grave provocation." North Korea claimed the three ships were only trying to wrangle Chinese fishing boats that were in the area illegally.
The two sides have been at war since the 1950's, as the Korean War ended in a truce — not a treaty.