North Korea claims its leader has put the military's rocket forces on standby to strike the United States. It is the latest threat from Pyongyang as tension continues to tighten on the Korean Peninsula.
South Korea's ministry of national defense says it cannot confirm a report of increased activity Friday among North Korea's mid-and-long range missile units. But it acknowledges intelligence officials of both South Korean and U.S. forces have increased monitoring of them.
The semi-official Yonhap news agency in Seoul quotes a military source saying "sharply increased movements of vehicles and soldiers have been detected recently at North Korea's mid and long-range missile sites."
This follows an announcement from Pyongyang quoting leader Kim Jong Un that "the time has come to settle scores with the U.S. imperialists" and the country's missile units are now on standby.
An announcer on Pyongyang Central Broadcasting Station says the country's supreme leader in a midnight emergency meeting ratified a firepower strike plan against the U.S. mainland, American bases in the Pacific -- including Hawaii and Guam -- and U.S. bases in South Korea.
The broadcast announcement said North Korea would attack should the United States "bring in enormous strategic armed forces and cause a reckless provocation."
A spokesman for South Korea's defense ministry Kim Min-seok, says this appears to be a North Korean propaganda exercise.
Kim says such operational orders, as a rule, would be conveyed confidentially. But, he says, reporting it publicly to let the entire world know seems like a psychological operation.
The emergency operations meeting in Pyongyang came in response to Thursday's flights of a pair of U.S. Air Force B-2 bombers over South Korea. The Pyongyang broadcast says the leader stated that the flights were an ultimatum that the United States "would start a nuclear war."
U.S. Defense Secretary Chuck Hagel denied the stealth bomber flights were intended as a provocation, but rather meant to assure U.S. allies in the region "that they can count on us to be prepared and to help them deter conflict."
The defense secretary says officials "every provocative, bellicose word and action" of the young third-generation leader who came to power at the end of 2011 has to be taken seriously.
"We've seen some historical trajectory here on where North Korea occasionally will go to try to get the attention of the United States, to try to maneuver us into some position favorably to them, whether it's more assistance or bilateral engagement," he said. "But the fact is that this is the wrong way to go. The action that he's taken and the actions they've taken and the words he's used, it is not going to project a more responsible, accountable relationship."
North Korea, in recent weeks, has threatened to launch a preemptive nuclear strike on the United States.
It is under various UN sanctions for its programs to develop nuclear weapons and ballistic missiles.
The reclusive and impoverished state is believed to have a small number of nuclear warheads but not the capability to effectively deploy them on long-range missiles.