(ATTN: UPDATES with more details in paras 6-9, 14; RECONSTRUCTS)
SEOUL, May 7 (Yonhap) -- North Korea fired an apparent submarine-launched ballistic missile (SLBM) in waters off its east coast Saturday, South Korea's military said, in the recalcitrant regime's latest saber-rattling that comes three days before President-elect Yoon Suk-yeol's inauguration.
The Joint Chiefs of Staff (JCS) said it detected the launch in waters off the North's eastern coastal city of Sinpo at 2:07 p.m. and that the missile flew some 600 kilometers at a top altitude of about 60 km.
The latest launch marks the North's 15th show of force this year. It came just three days after the reclusive regime test-fired what was thought to be an intercontinental ballistic missile (ICBM).
"The North's recent series of missile launches are acts of serious threat that undermine peace and stability on the Korean Peninsula and in the international community, and a clear violation of U.N. Security Council resolutions," the JCS said in a statement, urging Pyongyang to immediately stop them.
"Preparing against the possibility of an additional launch, our military is tracking and monitoring related movements, and maintaining a full readiness posture," it added.
The North last test-fired an SLBM in October last year. The test is known to have involved a so-called "mini-SLBM."
The intelligence authorities here are said to believe Saturday's launch involved an SLBM akin to the one fired in October.
The North's push for the SLBM project underscores its drive to diversify nuclear delivery vehicles, including ICBMs, observers said.
"The ability to launch ballistic missiles from a submarine would further complicate missions to neutralize and defend against North Korea's nuclear forces," Leif-Eric Easley, associate professor of international studies at Ewha Womans University, said.
Seoul and Washington have been keenly watching the North's quest to acquire an operational SLBM, seen as a formidable asset capable of launching surprise retaliatory nuclear attacks.
The SLBM is a bedrock asset for nuclear retaliation, as a submarine carrying it can operate undetected, launch counterstrikes and thus allow a country to survive an enemy's preemptive attack.
During a military parade last month, the North showcased a set of SLBMs, including the mini-SLBM.
At the parade, North Korean leader Kim Jong-un hinted his country could use nuclear arms in case of encroachment on its "fundamental rights," raising speculation he is shifting to a more aggressive doctrine for nuclear use.
Some observers said Saturday's launch could be an answer to Seoul's test-firing of two consecutive SLBMs last month, which signaled the South's SLBM was nearing its operational deployment.
Concerns have persisted that the North could continue to engage in provocations, such as another ICBM launch or a nuclear test, particularly around Yoon's inauguration slated for Tuesday or his summit with U.S. President Joe Biden scheduled for May 21.
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