A US Navy nuclear submarine arrived in South Korea hours after North Korea fired two new missiles.
Kim Jong-un launched two “new design” missiles on Thursday despite agreeing to start talks with US President Donald Trump again.
War submarine USS Oklahoma City (SSN-723) docked at the southern port of Busan the same day.
The 6,900-ton sub was there to replenish supplies and let its crew rest, US government sources said on Friday.
It is a Los Angeles-class submarine, a type of fast attack sub which carry about 25 torpedo tube-launched weapons, as well as Mark 67 and Mark 60 CAPTOR mines.
“We cannot but develop nonstop super-powerful weapon systems to remove the potential and direct threats to the security of our country that exist in the south”
Tensions seemed to have calmed down slightly between the US and North Korea after Kim Jong-un last month praised an “excellent letter” sent by Donald Trump.
But the rogue state then fired “unidentified projectiles” from its east coast, which were revealed to be a new design of missile, according to a defence source.
Launched from the coastal city of Wonsan, one missile flew 267 miles and the other 428 miles out over the sea.
They both reached an altitude of 30 miles before splashing down, an official at South Korea’s defence ministry told Reuters.
North Korea said its latest missile launch was a warning to South Korean “warmongers” to stop importing weapons and conducting joint military drills with the US.
Kim Jong-un personally watched the test-fire of two short-range ballistic missiles, which was also shown on state TV.
The missile tests raise doubts about the revival of denuclearisation talks, which stalled after the collapse of a second summit between Kim and Trump in Hanoi in February.
“We cannot but develop nonstop super-powerful weapon systems to remove the potential and direct threats to the security of our country that exist in the south,” Kim said, according to state news agency KCNA.