North Korea fired a ballistic from its capital Pyongyang towards the sea between the Korean Peninsula and Japan, South Korea's military has said.
Seoul's Joint Chiefs of Staff said the South Korean and US militaries were analysing the launch and did not immediately confirm how far the projectile travelled and where it landed.
The launch comes days after the North fired what was assessed as three short-range ballistic missiles into the sea and a month after its second flight test of an intercontinental ballistic missile, which analysts say could reach deep into the US mainland when perfected.
The North has also threatened to fire some of its missiles towards Guam and expressed anger over the ongoing annual war games between the United States and South Korea.
The new missile launch comes as North Korea wants to take its complaints about the war games to the UN Security Council, saying the annual manoeuvres are recklessly provocative at a time of tension.
The letter, dated Friday, asks Egypt as Security Council president to schedule a discussion urgently.
The Egyptian mission did not have any immediate comment on Monday.
Pyongyang regularly argues that the US-South Korean military exercises are an invasion rehearsal.
This year, they come after North Korean leader Kim Jong Un and President Donald Trump of the US traded warlike threats.
North Korea's UN ambassador, Ja Song Nam, writes in the letter that the exercises are "provocative and aggressive" when the Korean peninsula is "like a time bomb".
A spokeswoman for the US state department disputed that, saying the only purpose of the manoeuvres is to improve readiness to defend South Korea.
"Our annual joint military exercises are transparent, defence-oriented, andhave been carried out regularly and openly under the Combined Forces Command for roughly 40 years," said Grace Choi of the department's East Asian and Pacific Affairs Bureau.
Japanese officials said the missile flew over the northern Japanese island of Hokkaido and landed in the Pacific Ocean. There was no damage to ships or anything else reported. Japan's NHK TV said the missile separated into three parts.
South Korea's military said the missile flew 1,678 miles, with a height of 341 miles.
In the US, the Pentagon said it was still in the process of assessing the launch.
It said the North American Aerospace Defence Command had determined the missile launch did not pose a threat to North America.