Seoul, Oct 6 (IANS): South Korea, the United States and Japan staged another joint naval exercise in the East Sea on Thursday with a focus on countering nuclear and missile threats from North Korea.

The exercise involving the USS Ronald Reagan aircraft carrier strike group opened in the international waters of the sea hours after North Korea fired two short-range ballistic missiles, Seoul's military said.

Several warships, including South Korea's King Sejong the Great destroyer, the USS Benfold destroyer belonging to the USS Ronald Reagan aircraft carrier strike group, and Japan's Chokai destroyer, were mobilised, Yonhap news agency reported quoting the Seoul's military.

They simulated scenarios of North Korean ballistic missile launches and focused on detecting, tracking and intercepting them by sharing target information, it said.

The three countries held combined maritime drills in the East Sea on September 30 involving the nuclear-powered aircraft carrier in a show of force against the North's continued provocations.

It was redeployed to the waters Wednesday in response to the North's firing of an intermediate-range ballistic missile over Japan the previous day.