By David Chance and Phil Stewart
SEOUL/WASHINGTON (Reuters) - North Korea put its missile units on standby on Friday to attack U.S. military bases in South Korea and the Pacific, after the United States flew two nuclear-capable stealth bombers over the Korean peninsula in a rare show of force.
North Korean leader Kim Jong-un signed off on the order at a midnight meeting of top generals and "judged the time has come to settle accounts with the U.S. imperialists in view of the prevailing situation", the official KCNA news agency said.
The North has an arsenal of Soviet-era short-range Scud missiles that can hit South Korea and have been proven, but its longer-range Nodong and Musudan missiles that could in theory hit U.S. Pacific bases are untested.
On Thursday, the United States flew two radar-evading B-2 Spirit bombers on practice runs over South Korea, responding to a series of North Korean threats. They flew from the United States and back in what appeared to be the first exercise of its kind, designed to show America's ability to conduct long-range, precision strikes "quickly and at will", the U.S. military said.
The news of Kim's response was unusually swift.
"He finally signed the plan on technical preparations of strategic rockets of the KPA (Korean People's Army), ordering them to be on standby for fire so that they may strike any time the U.S. mainland, its military bases in the operational theaters in the Pacific, including Hawaii and Guam, and those in South Korea," KCNA said.
South Korea's Yonhap news agency reported there had been additional troop and vehicle movements at the North's mid- and long-range missile sites, indicating they may be ready to fire.
"Sharply increased movements of vehicles and soldiers have been detected recently at North Korea's mid and long-range missile sites," Yonhap quoted a South Korean military source as saying.
It was impossible to verify the report which did not specify a time frame, although South Korea's Defense Ministry said on Friday that it was watching shorter-range Scud missile sites closes as well as Nodong and Musudan missile batteries.
The North has launched a daily barrage of threats since early this month when the United States and the South, allies in the 1950-53 Korean War, began routine military drills.
The South and the United States have said the drills are purely defensive in nature and that no incident has taken place in the decades they have been conducted in various forms.
The United States also flew B-52 bombers over South Korea earlier this week.