North Korea test-fired a ballistic missile Wednesday from a submarine off its east coast, a South Korean military official said.
The launch comes at a time of heightened tensions between the two countries.
North Korea launched the missile from the coastal town of Sinpo, South Korea's Joint Chiefs of Staff said in a statement.
It is still unclear whether the launch was successful or not.
This isn't the first time North Korea has fired submarine-launched ballistic missiles into the sea. But so far, the country hasn't acquired missiles capable of striking targets as far away as the U.S. mainland.
North Korea launching missiles from submarines would be an alarming development because those are much more difficult to detect in advance.
This launch comes just days after the U.S. and South Korea began conducting their annual drills that are essentially a rehearsal in case North Korea ever decides to invade.
A spokesman for North Korea's military was recently quoted saying, it will "turn the stronghold of provocation into a heap of ashes through Korean-style pre-emptive nuclear strike" if the U.S. and South Korea "show the slightest sign of aggression."
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