North Korea has fired three short-range ballistic missiles into the sea off its east coast, the US military has said.
A spokesman for US Pacific Command, using times at its Hawaii-based headquarters, said: "The first and third missiles at 11.49am and 12.19pm failed in flight.
"The second missile launch at 12.07pm appears to have blown up almost immediately."
None of the missiles, launched from near Kittaeryong in the North, had posed a threat to either North America or the US Pacific territory of Guam, the spokesman added.
South Korean President Moon Jae-in said in response to the launches: "The military is keeping a tight surveillance over the North to cope with further provocations."
The launches come as tens of thousands of South Korean and US troops take part in joint military drills in the South, which Pyongyang views as a highly provocative rehearsal for an invasion of its own territory.
The 'Ulchi Freedom Guardian' war games are a largely computer-simulated exercise that runs for two weeks in the South. Pyongyang threatens strong military counter-action each year.
In recent weeks the North has threatened to fire a salvo of missiles toward Guam, but has since backed away from the plan and tensions have eased.
Under Mr Kim, Pyongyang has made rapid strides in its ballistic missile technology, which it is banned from pursuing under United Nations resolutions.
Last month, it carried out two successful intercontinental ballistic missile (ICBM) launches, overseen by Mr Kim and apparently bringing the US into range for the first time.
President Donald Trump had warned he would unleash "fire and fury" if the North continued its provocation.