South Korea Tuesday staged live-fire artillery exercises on two frontline islands near the tense border with North Korea, including one that was hit by a deadly barrage from the North last November. The one-day \"regular\" exercises went ahead on Baengnyeong and Yeonpyeong islands in the Yellow Sea without incident, a defence ministry spokesman told AFP without giving details. Yonhap news agency, quoting military sources, said marines would fire K-9 self-propelled howitzers, Vulcan cannon and 81mm mortars during the two-hour drill. About 10 US military officers would attend the exercises as observers, it said. A similar South Korean drill last November was answered by a North Korean artillery and rocket attack on Yeonpyeong island, which killed two marines and two civilians. The North said it was responding to the South\'s \"provocative\" drill, which dropped shells into waters it claims around the disputed border. The South said its exercise was routine, with weapons pointed away from the North\'s coastline. Tuesday\'s drills were the second live-fire exercise on the two islands this year. The previous one passed without incident despite threats from the North to hit back. Tensions along the Yellow Sea border have been acute since the shelling, the first attack on a civilian-populated area in the South since the 1950-53 war. The South also accuses the North of torpedoing a warship near the border in March 2010 with the loss of 46 sailors. The North denies involvement in the sinking.