North Korea on Friday threatened to respond decisively if South Korean forces carry out live-fire drills near the disputed maritime border as planned, according to dpa. Seoul announced Thursday it would hold a day of artillery exercises on Yeonpyeong island, which recently came under attack from the North, some time between Saturday and Tuesday. If the planned drills go ahead, "second and third self-defensive blows that cannot be predicted will be dealt," North Korea said in a statement carried by the official Korean Central News Agency. Pyongyang said its retaliation would be "more serious" than on November 23, when it shelled Yeonpyeong, killing two soldiers and two civilians, and injuring 18 others. The navies of South Korea and its ally the United States have conducted several maritime drills around the peninsula since November's incident, over repeated objections from the North. The South Korean Joint Chiefs of Staff said the upcoming manoeuvres were part of routine exercises. Spokesman Colonel Lee Bung Woo said the artillery pieces on the island would not be pointed at North Korea. Pyongyang has argued that any shells hitting the water around the island fall on its territory, saying that the border was drawn up unilaterally by the US after the 1950-53 conflict between the Koreas ended in a ceasefire, leaving the two countries technically at war.