South Korea and the US have begun three days of naval exercises in what is being seen as a show of force aimed at North Korea.
The scheduled drills, involving a US nuclear submarine, come after North Korea said it was planning to carry out its third test of a nuclear device.
The US and South Korea have promised “significant consequences” if it goes ahead with the underground explosion.
The North has criticised the naval drills as “war-mongering”.
Read more at BBC News