The United States and South Korea have launched their large-scale military drills in the Sea of Japan. It's a move that is feared may further complicate the security situation in the region. The four-day drills, code-named "Invincible Spirit", will run until Wednesday.

US military officials say the maneuvers aim at detecting and defeating submarines intruding into the seas east of the Korean peninsula.

Lieutenant General Jeff Remington, US Air Force, said, "Invincible Spirit is defensive in nature, and designed to dissuade and deter further provocation from North Korea."

South Korea is accusing the DPRK of torpedoing its warship, killing 46 sailors. The DPRK is denying any involvement in the sinking.

Lieutenant General Jeff Remington, said, "The Republic of Korea Air Force and the United States are committed to providing the right combat power with the necessary fire power to protect the Republic of Korea and regional stability."

The war games involve the Nimitz-class aircraft carrier USS George Washington, 20 ships and submarines and 200 aircraft, with about 8-thousand US and South Korean sailors taking part.

The George Washington has left the port of Busan to join in the exercise. It is one of the biggest ships in the US Navy. It is a potent symbol of American military power. with about five-thousand sailors and aviators and able to carry up to 70 planes.

The US air forces F-22 Raptor, the world's most advanced military aircraft, was also shown at the US Osan Air Base. south of Seoul.

F-22 can detect missiles and can evade missile launch sites by using its radars. It will be employed in South Korea for the first time.

Jet fighters being refuelded by tanker planes were also shown to media as part of the drill.