The United States said two nuclear-capable B-2 stealth bombers flew "deterrence" missions over South Korea on Thursday, defying apocalyptic threats of retribution from North Korea against ongoing war games.

The deployment of the stealth bombers was intended to send a potent message to Pyongyang about the U.S. commitment to defending South Korea against any aggression, as military tensions on the Korean peninsula soar.

It came shortly after the North severed its last-remaining military hotline with South Korea and put its rocket units on combat status with a threat to target U.S. bases in the Pacific region. The two B-2s, from Whiteman Air Force Base in Missouri, flew the 13,000-mile round-trip in a "single continuous mission", dropping dummy ordnance on a target range in the South, the U.S. military said in a statement.

"This... demonstrates the United States' ability to conduct long-range, precision strikes quickly and at will," the statement said.

The bombers were participating in South Korean-U.S. military exercises that have incensed North Korea, which has threatened to unleash a second Korean War and launch pre-emptive nuclear strikes on South Korea and the US mainland.AFP