South Korea's military conducted a live-fire artillery drill on Wednesday on a border island shelled by North Korea last November, officials said, the second firing drill since the North's bombardment that inflamed tensions.

   The firing exercise was started by marines on Yeonpyeong Island, near the tense Yellow Sea border with North Korea, at around 9:30 a.m. and was scheduled to last for about three hours, said Col. Lee Bung-woo, a spokesman at the South's Joint Chiefs of Staff (JCS).

   Another firing drill took place on Baengnyeong Island, the closest island to the sea border, on the same day, Lee said.

   "These exercises are being staged as part of our military's routine drills," Lee said, adding the South's military has not detected any unusual military movements by the North's armed forces.

   Air Force fighter jets were on standby in the air in case of any contingency, Lee said.

   "We will continue to conduct live-fire drills on border islands on a regular basis to bolster military capabilities there," he added.

   As always, JCS officials said, the artillery guns on the islands were aimed south, away from North Korea.

   K-9 self-propelled howitzers, 81-millimeter mortar guns and Vulcan guns were mobilized for the drills, according to the official.

   Four South Koreans -- two marines and two civilians -- were killed in the North's Nov. 23 shelling on Yeonpyeong Island.

   Pyongyang claims its artillery strike on Yeonpyeong was in self-defense because it was provoked by Seoul's live-fire drill near the island. Seoul said the drill was part of routine training and no shells landed in the North's territory, accusing Pyongyang of a premeditated attack.

   The South's military held a live-fire drill on Yeonpyeong on Dec. 20 amid the North's pledge of retaliation. Later in the day, the North said it would not retaliate over the drill, saying it was "not worth reacting."