The Republic of Korea (ROK) and United States on Sunday launched a four-day joint naval drill in tense waters west of the divided Korean Peninsula.

The drill, conducted five days after the artillery skirmish between South Korea and the Democratic People's Republic of Korea (DPRK) off the west coast, is centering on antiaircraft defense and naval surface warfare.

Calling the drill "defensive in nature", the U.S. Forces Korea (USFK) here said in a statement it "demonstrates the strength" of the alliance between Seoul and Washington and their "commitment to regional stability through deterrence." It is also designed to improve the two nation's military interoperability, it said.

According to reports, the USS George Washington, a nuclear- powered 97,000-ton carrier is taking part in the drill, along with the USS Cowpens cruiser, the USS Stethem destroyer, the USS Fitzgerald and the USS Shiloh.

The South Korean military sent two destroyers, a naval patrol ship and an antisubmarine warfare aircraft to take part in the exercise.

China has expressed its opposition to any military operations in its exclusive economic zone without permission.