North Korea launched a missile early on Sunday, but it reportedly "blew up almost immediately" on take off, according to the US military.
The reported test launch came a day after North Korea held a massive military parade in its capital, Pyongyang, marking the birth anniversary of the state founder, where what appeared to be new ballistic missiles were displayed.
The attempted blast off near Sinpo, on North Korea's east coast, is believed to have failed shortly after launch, South Korean and US officials said.
There were no further details, and the office said it was analysing the launch.
The US Pacific Command detected and tracked what it assessed to be a North Korean ballistic missile launch early on Sunday, said Navy Commander Dave Benham, a military spokesman.
"The missile blew up almost immediately," Benham said. "The type of missile is still being assessed."
Citing the military parade and the launch of the missile, South Korea's foreign ministry said in a statement that the North's combined show of force "threatened the whole world".
There was no immediate response from Pyongyang.
Fears have been growing that the reclusive North could soon conduct its sixth nuclear test or more missile launches in defiance of United Nations sanctions and stark warnings from the US that a policy of patience was over.
The North launched an intercontinental ballistic missile (ICBM) from the same region earlier this month ahead of a summit meeting between the leaders of the US and China, its key ally, to discuss the Pyongyang's increasingly defiant arms programme.
The White House has said US President Donald Trump has put the North "on notice", while the possibility of American military action against Pyongyang has gained traction following US cruise missile strikes against Syria on April 7.
Trump has ordered a navy strike group flagshipped by a nuclear-powered aircraft carrier to head to the region as a show of force as his officials assess tougher economic sanctions, as well as military options against the North.
The North has in turn warned of a nuclear strike against the US if provoked.
Pyongyang says it has developed and would launch a missile that can strike the mainland US, but officials and experts believe it is some time away from mastering all the necessary technology.
James Mattis, the US defence chief, said in a statement on Sunday: "The president and his military team are aware of North Korea's most recent unsuccessful missile launch. The president has no further comment."