SEOUL: South Korean marines in amphibious armoured vehicles waded ashore under the guns of patrolling warships on Wednesday as part of large-scale military exercises that organizers say are necessary to prepare for any North Korean threats.

The amphibious landing practice, held near Pohang on South Korea's east coast, is part of the 12-day Hoguk 22 field exercises, which have included some drills with U.S. troops, such as a river-crossing exercise last week.

"Our goal is to be equipped with immediate response capabilities, regardless of time, location and circumstances if we are tasked with a mission," South Korean Marine Corps Colonel Kim Tae-won told reporters.

Overall, thousands of South Korean troops have been mobilized for the drills, according to the military.

North Korea has condemned the drills for raising tensions and has test-fired rockets and artillery in response. South Korea and the United States say the exercises are defensive, and necessary for deterring the North.

The United States, Japan and South Korea warned on Wednesday that an "unparalleled" scale of response would be warranted if North Korea conducts a seventh nuclear bomb test.

The United States and its allies believe North Korea could be about to resume nuclear bomb testing for the first time since 2017.