South Korea and the United States on Wednesday wrapped up the four-day joint military drills.

The two allies continued with anti-submarine exercises in waters off the east coast of the divided Korean Peninsula on the last day of the drills, in which the two nations' troops practiced transporting logistical support for the soldiers when they face aerial, underwater and maritime threats from enemy.

Code-named "Invincible Spirit," the four-day naval and air maneuvers, starting from Sunday and involving 20 ships and submarines, 200 aircraft and 8,000 troops from the two nations, included anti-submarine drills, naval live-fire exercises, aerial training and computer-based simulation exercises.

It was the first in a series of similar joint exercises to be conducted in coming months, part of military "countermeasures" against the Democratic People's Republic of Korea (DPRK), who was blamed for sinking a South Korean warship with a torpedo in March, which took 46 lives of South Korean sailors. But Pyongyang denied any involvement.

Apart from the annual Ulchi Freedom Guardian exercises between Seoul and Washington, which will take place in the period from Aug. 16 to Aug. 26, the two allies will also stage joint military drills in waters off the west coast of the Korean Peninsula in September, and will conduct similar drills every month till the end of this year, in a bid to "prevent the warship sinking case from recurrence", local media reported, citing senior military sources.

In response, the DPRK on Tuesday said it did not fear "military threats" and "warnings" by the United States and South Korea, calling the war games, planned maneuvers for later this year and new sanctions threats against Pyongyang were "serious provocations " to the DPRK and "rude challenges" to the international community appealing for peace. Pyongyang also threatened a "retaliatory sacred war" against the show of joint military prowess.

China has also expressed its concern over the drills near the country, urging relevant parties to "remain calm and exercise restraint and not do anything to exacerbate regional tensions."