But South Korean analysts said Kim decided not to conduct the nuclear test, instead holding a parade meant to show off North Korea's military might.
North Korean leader Kim Jong Un presided over the massive parade in the capital of Pyongyang.
The White House has said US President Donald Trump has put the North "on notice" while the possibility of US military action against Pyongyang has gained traction following US strikes against Syria on April 7.
"The North attempted to launch an unidentified missile from near the Sinpo region this morning but it is suspected to have failed", South Korea's Office of the Joint Chiefs of Staff said in a statement.
Kim Jong-un reviews the parade featuring new long-range missiles.
Kim was greeted Saturday with thunderous applause as he stepped into view on a large podium, clapping to acknowledge the thousands of soldiers and civilians taking part in the parade at Kim Il Sung Square.
According to the Wall Street Journal, an expert on North Korean weaponry said the missiles appeared to be extremely advanced, calling the new long-range missile-a newly-modified intercontinental ballistic missile (ICBM) with elements of two other ICBMs-a "frankenmissile".
Despite speculation that the country would launch a nuclear test in celebration of its founder's birth on Saturday, North Korea declined to do so.
"If the United States wages reckless provocation against us, our revolutionary power will instantly counter with annihilating strike, and we will respond to full out war with full out war and to nuclear war with our style of nuclear strike warfare".
In the latest, China has warned North Korea of a war as a reaction to its "merciless" response to the U.S.
Also on Friday, North Korea's vice foreign minister said that Trump's tweets he recently tweeted, for example, that the North is "looking for trouble" have inflamed tensions.
During a speech at the parade, a high-ranking North Korean official blamed the Trump administration for heightened tensions on the Korean peninsula, saying North Korea will respond with "all-out war and a nuclear war" if attacked.
North Korea, still technically at war with South Korea after their 1950-53 conflict ended in a truce, but not a treaty, has on occasion conducted missile or nuclear tests to coincide with big political events.
A submarine-launched ballistic missile was displayed at the parade for the first time.
Unlike at some previous parades attended by Kim, there did not appear to be any senior Chinese official in attendance.
NY [U.S.A.], April 15: Air China has made a decision to suspend its flights between Beijing and North Korean capital Pyongyang. Analysts say the missiles could one day be capable of hitting targets as far as the United States, although North Korea has yet to flight-test them.
During his New Year's address, Kim said the country's preparations for an ICBM launch had "reached the final stage".
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