North Korea has made a failed attempt to launch a missile just hours after telling the US it was prepared for war.
The launch attempt took place in the Sinpo area of the North, a day after a huge military parade took place in Pyongyang.
The US military said the launch took place at 10.21pm UK time (5.51am local time) but the missile "blew up almost immediately".
US officials said they are certain the missile was not an Intercontinental Ballistic Missile (ICBM).
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They added that the missile was launched from land, rather than a ship or submarine.
There had been fears of an attempted missile launch as Saturday was the 105th anniversary of the birth of the country's founder.
South Korea's defence ministry said in a statement: "North Korea attempted to test an unidentified type of missile from Sinpo area in the South Hamkyong Province this morning, but we suspect the launch has failed."
The White House said US Vice President Mike Pence, who arrived in South Korea on Sunday as part of a tour of Asia, has been briefed.
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Secretary of Defence James Mattis said President Donald Trump is also aware of the launch.
The North launched a ballistic missile from the same region earlier this month ahead of a summit between the the US and China.
On that occasion a ballistic missile flew for about 37 miles (60km) before landing in the Sea of Japan.
Mr Trump has put Pyongyang "on notice" over fears the country is developing a weapon that could threaten the US.
On Saturday morning, North Korea warned America to end its "military hysteria" or face retaliation.
The reclusive state said it was prepared to respond to any attacks with "nuclear attacks of our own style".
North Korea's Supreme Leader presided over a military parade marking the "Day of the Sun", the 105th birthday of Kim Il-Sung.
Goose-stepping soldiers and marching bands filled the square, next to the Taedonggang River that flows through Pyongyang.
Tanks, multiple rocket launch systems and other weapons followed, while single-engine planes flew in a 105 formation overhead.
China, Pyongyang's sole major ally, has warned that the tensions must be stopped from reaching an "irreversible and unmanageable stage".
The US, which has moved an aircraft carrier and several other warships towards the Korean peninsula, has previously warned that its policy of "strategic patience" with North Korea is over.
The UK Foreign Office said it was "concerned by reports of a missile test by North Korea" and was "monitoring the situation closely".