Three of the four missiles came down provocatively close to US ally Japan, in waters that are part of its exclusive economic zone, representing a challenge to US President Donald Trump.
Washington and Tokyo have sought an emergency meeting of the UN Security Council to discuss the launch, likely to be scheduled for tomorrow.
Under UN resolutions, Pyongyang is barred from any use of ballistic missile technology, and the US ambassador to the UN, Nikki Haley, said on Twitter that the world “won’t allow” North Korea to continue on its “destructive path”.
But six sets of UN sanctions since its first nuclear test in 2006 have failed to halt its drive for what it insists are defensive weapons.
Kim Jong-Un gave the order for the drill to start, the North’s official Korea Central News Agency (KCNA) reported.
“Feasting his eyes on the trails of ballistic rockets”, he praised the Hwasong artillery unit that carried it out, it said.
“The four ballistic rockets launched simultaneously are so accurate that they look like acrobatic flying corps in formation, he said,” the agency added, referring to Kim.
The military units involved are “tasked to strike the bases of the US imperialist aggressor forces in Japan in contingency”, KCNA said.
But a US defence official told AFP that North Korea had launched five extended-range Scud missiles yesterday, with one crashing somewhere over the Korean peninsula.
Seoul and Washington last week began annual joint military exercises that always infuriate Pyongyang.
Kim Jong-Un ordered his military “to keep highly alert as required by the grim situation in which an actual war may break out anytime”, KCNA reported, and to be ready to “open fire to annihilate the enemies” when ordered.
Pyongyang regularly issues threats against its enemies, and carried out two atomic tests and a series of missile launches last year, but yesterday was only the second time its devices have come down in Japan’s EEZ.
The launches came ahead of a trip by new US Secretary of State Rex Tillerson to the region.
UN Secretary-General Antonio Guterres also condemned them, urging Pyongyang to refrain from further “provocations”.
Trump has described North Korea as a “big, big problem” and vowed to deal with the issue “very strongly”.
White House spokesman Sean Spicer said yesterday that North Korea poses a “very serious threat”, adding the administration was taking steps to “enhance our ability to defend against North Korea’s ballistic missiles”.
South Korea said yesterday that four missiles were fired from Tongchang County in North Pyongan province into the East Sea—its name for the Sea of Japan—travelling about 1,000 kilometres and reaching an altitude of 260 kilometres.