A joint drill with U.S. forces off the east coast of South Korea on Tuesday featured naval cannons fired from ships and the dropping of depth charges.
Warships fired weapons and dropped anti-submarine bombs in the Sea of Japan during the third day of the four-day exercise, South Korean Defense officials say. They say the target was an abandoned submarine meant to simulate a submerged North Korean vessel. It is part of the largest show of force in the region jointly by the U.S. and South Korea in a number of years.
Tensions have been on the rise following an incident in the Yellow Sea four months ago when a South Korean warship exploded and sank, killing 46 sailors. South Korea, the United States and other countries which took part in the subsequent investigation concluded the Cheonan warship was hit by a North Korean torpedo. North Korea denies responsibility.
In all, about 20 naval vessels of the two countries are involved in the current war game. Tuesday's live-fire drill took place about 120 kilometers east of the Korean peninsula and well south of North Korea's territorial waters.
There is also an aerial component involving 200 aircraft, including the most sophisticated U.S. fighter jets, as well as airborne electronic surveillance platforms.
Rear Admiral Dan Cloyd is the top-ranking U.S. military officer participating in the exercise.
From on board the USS George Washington aircraft carrier, he tells VOA News that in addition to improving war-fighting skills and coordination with South Korean forces, there is another element specifically with North Korea in mind.
"That we've achieved the deterrent effect with respect to North Korea and will give them pause as they make decisions about the future of their nation and how they conduct themselves on the international stage," he said.
The war games are overshadowing the 57th anniversary of the armistice that halted the three-year Korean war. There has never been a peace treaty and thus the Korean peninsula technically remains in a state of war.
The United Nations command held a ceremony Tuesday marking the armistice anniversary at the truce village of Panmunjom in the Demilitarized Zone.
The commander of U.S. Forces in Korea, General Walter Sharp, made a direct appeal to Beijing for help in quelling North Korean aggression.
"I ask all countries, especially China, to work together responding to North Korean provocations," he said. "All nations should assist in convincing North Korea that its path to security and prosperity lies in cessation of its provocative behavior, better relations with its neighbors and complete irreversible de-nuclearization."
North Korea staged a mass indoor ceremony in Pyongyang Monday to mark the armistice anniversary. Its armed forces minister, Kim Yong-chun, vowed to mobilize his country's military might, including its "nuclear deterrence" to destroy opposing forces if the U.S.-South Korean joint exercises continue.
Kim says the situation has been driven to the brink and war could easily erupt at any time.
Military officials here in the South Korean capital say they have detected no signs of unusual military activity in the North during this week's joint exercise.