South Korea on Tuesday said it had lodged a formal protest with North Korea over its recent coastal artillery drills, revealing the exercise had been staged on the ninth anniversary of the North's bombardment of Yeonpyeong island.In a regular briefing, Ministry of National Defense (MND) spokesperson Choi Hyun-soo said the South had taken countermeasures in response to the North's live-fire exercise, conducted near the inter-Korean maritime border on Changrin island.“We strongly remonstrated the North this morning about its coastal artillery firing exercise through a communication line in the western district,” Choi said.The South verbally lodged the protest