The missile was believed to be a Scud-class ballistic missile and appeared to have landed in Japan's exclusive economic zone, South Korean officials said.
North Korea fired what appeared to be a short-range ballistic missile on Monday that landed in the sea off its east coast, the latest in a series of missile tests defying world pressure and threats of more sanctions.
The missile was believed to be a Scud-class ballistic missile and flew about 450 km (280 miles), South Korean officials said.
Monday's launch follows two successful tests of medium to long-range missiles in as many weeks by Pyongyang, which has been conducting such tests at an unprecedented pace in an effort to develop an intercontinental ballistic missile (ICBM) it says will be capable of hitting the mainland United States.
It is the third test-launch since South Korea's liberal President Moon Jae-in took office on May 10 pledging to engage Pyongyang in dialogue. Moon says sanctions alone have failed to resolve the growing threat from the North's advancing nuclear and missile programme.
North Korea, which has conducted dozens of missile tests and tested two nuclear bombs since the start of 2016 in defiance of UN Security Council resolutions, says the programme is necessary to counter US aggression.
TRT World spoke with Seoul-based journalist Joseph Kim for more.
The White House said President Donald Trump had been briefed on the launch. The US Pacific Command said it tracked what appeared to be a short-range ballistic missile for six minutes and assessed it did not pose a threat to North America.
The US has said it was looking at discussing with China a new UN Security Council resolution and that Beijing, the main diplomatic ally of Pyongyang, realises time was limited to rein in the North's weapons programme through negotiations.
US Defense Secretary Jim Mattis, asked what a military conflict with North Korea might look like if diplomacy failed, warned on Sunday that would be "probably the worst kind of fighting in most people's lifetimes."
"The North Korean regime has hundreds of artillery cannons and rocket launchers within range of one of the most densely populated cities on Earth, which is the capital of South Korea," Mattis told CBS news programme "Face the Nation."
"And in the event of war, they would bring danger to China and to Russia as well."
Test new capabilities
Japan lodged a protest against the North's latest missile launch which appeared to have landed in Japan's exclusive economic zone.
Japanese Prime Minister Shinzo Abe vowed action along with other nations to deter Pyongyang's repeated provocation.
"We will never tolerate North Korea's continued provocations that ignore repeated warnings by the international community," Abe told reporters.
"As agreed during the G7 summit, the North Korean problem is the international community's top priority. In order to deter North Korea, we will take concrete action with the United States," he said.
Seoul's new liberal administration has said Pyongyang's repeated test launches were dashing hopes for peace on the Korean Peninsula.
South Korea's Moon swiftly called a meeting of the National Security Council, South Korea's Office of the Joint Chiefs of Staff said in a statement.
North Korea last test-fired a ballistic missile on May 21 off its east coast and on Sunday said it had tested a new anti-aircraft weapon supervised by leader Kim Jong-un.
North Korea has tested Scud-type short-range missiles many times in the past, most recently in April according to US officials. But experts say it may be trying to test new capabilities that may be fed into its efforts to build an ICBM.
"There are many possibilities … It could have been a test for a different type of engine. Or to verify the credibility of the main engine for ICBM's first stage rocket," said Kim Dong-yub, a military expert at Kyungnam University's Far Eastern Studies in Seoul.
Modified versions of the Scud have a range of up to 1,000 km (620 miles).
On Tuesday, the US will test an existing missile defence system to try to intercept an ICBM, the first such test, officials said last week.