South Korea will hold military exercises in the next few days in the area shelled by North Korea last month, according to reports.
The defense ministry said artillery guns on the island would be aimed away from North Korea, as usual during such tests, and that they would "react firmly and strongly" to any North Korean provocation.
North Korea cited a similar drill on the Yellow Sea island, called Yeonpyeong, as the reason it opened fire Nov. 23, killing four South Koreans and damaging nearly every building in the island's main village, home to 1,400 people.
It was the first attack on South Korean land by the North since the Korean War of the 1950s.
South Korea said reporters and observers from the United Nations Command, responsible for overseeing the 1953 armistice agreement that ended hostilities between the North and South, would be invited to witness the drill.
Pyongyang has said that the waters around the island belong to it and that such South Korean artillery tests infringe on its territory. North Korea has disputed the inter-Korean maritime border in the Yellow Sea — drawn by the United Nations as part of the armistice — since the 1990s.
As if in preparation, South Koreans staged their biggest-ever evacuation drill Wednesday, with citizens stopping their cars, donning gas masks and ducking into underground shelters. The government hopes to prepare traditionally indifferent citizens for attack by the North.
The rise in tensions comes as New Mexico Governor Bill Richardson arrived in Pyongyang. Richardson often has acted as a diplomatic troubleshooter and has made regular visits to North Korea.