Seoul and Tokyo call national security meetings in respective countries after the latest test by Pyongyang.
North Korea fired a ballistic missile on Friday from its northern Jangang province that landed in the sea off its east coast, possibly in Japan's exclusive economic zone, South Korea and Japan said.
The launch took place at 11:41 pm (1441 GMT), an official at South Korea's Office of the Joint Chiefs of Staff said. The US Department of Defense also confirmed the launch as a ballistic missile, saying it was making further assessments.
"As a result of their launches of ICBM-level missiles, this clearly shows the threat to our nation's safety is severe and real," Japanese Prime Minister Shinzo Abe said.
Japanese Chief Cabinet Secretary Yoshihide Suga said that the North Korean missile flew for about 45 minutes. Japanese broadcast NHK citing a military official said the missile reached an altitude of more than 3,000 km (1,860 miles).
The data indicates the missile was fired at a sharply lofted angle but packed more power than a missile launched earlier this month that US and South Korean officials said was an intercontinental ballistic missile (ICBM), potentially capable of hitting the mainland United States.
The North claimed after the July 4 launch that it had successfully tested an ICBM that flew 933 km (580 miles), reaching an altitude of 2,802 km (1,741 miles) over a flight time of 39 minutes and able to carry a large and heavy nuclear warhead.
US–based missile expert Michael Elleman of the International Institute for Strategic Studies said Friday's test was possibly of a similar missile with a more powerful second stage but stressed it was a preliminary assessment.
South Korean President Moon Jae-in has called a National Security Council meeting for 1 a.m. Saturday, his office said, and Abe also said a National Security Council meeting would be convened.