Kim Hjelmgaard, USA TODAY
North Korea on Tuesday said it was putting its long-range rocket units on the highest possible combat-posture level and threatened strikes targeting Guam, Hawaii and the U.S. mainland.
The news was released by the North's Korean Central News Agency on the third anniversary of a suspected North Korean torpedo attack on a South Korean warship that killed 46 South Korean sailors. North Korea denies the warship sinking.
On Tuesday, the North Korean army's Supreme Command said it will take "practical military action" to protect national sovereignty and its leadership in response to what it called U.S. and South Korean plots to attack.
"From this moment, the Supreme Command of the Korean People's Army will be putting in combat duty posture No. 1 all field artillery units including long-range artillery units strategic rocket units that will target all enemy object in U.S. invasionary bases," the KCNA news agency said.
Officials in South Korea said no suspicious activity in the North had been detected.
The two Koreas have clashed repeatedly in recent years and North Korea has vowed in the past to turn Seoul into a "sea of fire."
North Korea has expressed anger over recent joint military drills by the U.S. and South Korea and crippling United Nations-endorsed sanctions in the wake of the North's Feb. 12 nuclear test.
The country has made nuclear threats against the U.S. and its allies in the past.
It is not clear if it has the technological capacity to do so.
The North's recent threats are seen partly as efforts to strengthen internal loyalty to young leader Kim Jong Un and to build up his military credentials.
Kim "needs to show he has the guts. The best way to do that is to use the military might that he commands," said Lee Yoon-gyu, a North Korea expert at Korea National Defense University in Seoul. "This paves the way for greater praise for him if North Korea makes a provocation later and claims victory."
China's foreign ministry appealed on Tuesday for all sides in the Korean peninsula to exercise restraint, according to Reuters.
Contributing: Associated Press