South Korea fires first submarine-launched ballistic missile

The test, supervised by President Moon Jae-in, came hours after nuclear-armed North Korea fired two ballistic missiles into the sea, according to the South's military -- prompting Washington to brand Pyongyang's action a provocative "threat" to Asian neighbors.

South Korea's test is a strategic advance for Seoul. It has been strengthening its military capabilities to counter the threat posed by the North, which is under international sanctions for its nuclear weapons and ballistic missile programs.

"It's extraordinary timing that you have not one but two Koreas testing ballistic missiles on the same day," Yonsei University professor John Delury told AFP.

"It does speak to the fact that there's an arms race in this region that everyone needs to pay attention to."

The South's missile was fired underwater from its newly commissioned submarine Ahn Chang-ho, and flew the planned distance before hitting its target, the presidential Blue House said.

With the successful tests, South Korea now has "sufficient deterrence to respond to North Korea's provocations at any time", Moon said, adding that his country should continue increasing its weapons programmes to "overwhelm North Korea's asymmetric power".