The U.S. military says it dispatched war planes to the Korean peninsula as a show of deterrence directed at North Korea.
The strategic B-2 bombers flew 20,000 kilometers non-stop Thursday from an air force base in the central U.S. to an island off the southwestern coast of the Korean peninsula before returning to their home base.
The mission was held amid increasing threats by North Korea against South Korea and the United States. Pyongyang has severed all communication links with South Korea, the United Nations and the Red Cross. But a tense border crossing was operating as usual Thursday at the Kaesong industrial complex.
In Washington, U.S. Defense Secretary Chuck Hagel linked the B-2 flights to recent North Korean provocations, which include threats from Pyongyang to launch nuclear strikes on South Korea, the United States and its Pacific allies.
Hagel told reporters "we have to take seriously every provocative, bellicose word and action that this new young leader [North Korea's Kim Jong-un] has taken so far" since coming to power.
The North Korean threats follow new United Nations sanctions against the North for conducting its third nuclear test in defiance of U.N. resolutions.
Pyongyang, which drew international condemnation after its February 12 nuclear test, has since railed almost daily against the U.N. sanctions imposed in response to the underground blast.
Tensions on the Korean peninsula are at their highest in years, with both the North and the U.S.-backed South demonstrating their military preparedness during military exercises.
Earlier this week, Pyongyang's powerful military command placed all North Korean missile and artillery units on "highest alert," in what it says is preparation for strikes on the United States and South Korea.
Pyongyang has gone so far as to threaten the United States with nuclear strikes and said its targets included U.S. assets in Guam, Hawaii and Japan.
Analysts say Pyongyang does not currently have the capability to mount an operational nuclear warhead on a missile. But many of its neighbors are worried that they may be easier targets for Pyongyang's conventional weapons.