The missile was launched from North Korea's Jangang province
North Korea has fired a ballistic missile into the Sea of Japan, officials in Tokyo and Washington say.
The missile was launched from North Korea's Jangang province at 11.40pm local time (2.40pm GMT) and flew for 45 minutes, before landing off the country's east coast.
Japanese Prime Minister Shinzo Abe held an emergency meeting to discuss the launch, while South Korean President Moon Jae-in has called a National Security Council meeting.
Japanese Chief Cabinet Secretary Yoshihide Suga described the launch as a "clear violation of UN resolutions", adding that his country "cannot tolerate North Korea's repeated provocations".
The Pentagon said it is assessing the situation and "will have more information soon".
The launch comes less than a month after the reclusive state tested its first long-range missile, which was allegedly capable of carrying a "large, heavy nuclear warhead".
Analysts said the "landmark" Hwasong-14 missile, which flew for around 40 minutes, could reach Alaska.
The missile test was described by US Secretary of State Rex Tillerson as a "new escalation of threat" to the world, while President Donald Trump called on China to "put a heavy move on North Korea and end this nonsense once and for all".