Fighter jets buzzed the skies and submarines cruised underwater as a flotilla of U.S. and South Korean warships led by a nuclear-powered U.S. supercarrier began exercises that have enraged North Korea.
U.S. officials denied North Korea's claims the manoeuvrs off Korea's east coast were a provocation, but said they were meant to send a strong message over the sinking of a South Korean warship in March that left 46 sailors dead.
The drills, which began Sunday and are set to run through Wednesday, involve about 8,000 U.S. and South Korean troops, 20 ships and submarines and 200 aircraft. The USS George Washington, with several thousand sailors and dozens of fighter jets aboard, was deployed from Japan.
"We are showing our resolve," said Capt. David Lausman, the carrier's commanding officer.
The exercises will be the first in a series of U.S.-South Korean manoeuvrs conducted in the East Sea off Korea and in the Yellow Sea closer to China's shores in international waters.
The exercises also are the first to employ the F-22 stealth fighter -- which can evade North Korean air defences -- in South Korea.
North Korea has called the drills an "unpardonable provocation" and threatened to retaliate with "nuclear deterrence" and "sacred war."
The North routinely threatens attacks whenever South Korea and the U.S. hold joint military drills, which Pyongyang sees as a rehearsal for an invasion. The U.S. keeps 28,500 troops in South Korea and another 50,000 in Japan, but says it has no intention of invading the North.
Still, the North's latest rhetoric carries extra weight following the sinking of the Cheonan warship in late March.
Washington and Seoul blame Pyongyang for the sinking of the 1,200-ton Cheonan warship near the Koreas' maritime border. A five-nation team of investigators concluded a North Korean torpedo sank the Cheonan, considered the worst military attack on the South since the 1950-53 Korean War.
North Korea, which denies any involvement in the sinking, has warned the United States against attempting to punish it.
"Our military and people will squarely respond to the nuclear war preparation by the American imperialists and the South Korean puppet regime with our powerful nuclear deterrent," the North's government-run Minju Joson newspaper said in a commentary headlined, "We also have nuclear weapons."
The commentary was carried by the official Korean Central News Agency.
Pyongyang's rhetoric was seen by most as bluster, but its angry response to the manoeuvrs underscores the rising tension in the region.
The George Washington, one of the biggest ships in the U.S. Navy, is a potent symbol of American military power, with about 5,000 sailors and aviators and the capacity to carry up to 70 planes.
The deployment of the supercarrier to the area off Korea was also raising eyebrows in China -- which was believed to have been concerned about having the carrier operate too close to its own shores.
