In response to the test, South Korea conducted a drill simulating an attack on its neighbour.
Sunday’s detonation was the North’s strongest ever, with the South measured the test at 50 kilotons.
South Korea’s defence ministry said in a parliament hearing that it was still detecting signs that Pyongyang plans to stage more ballistic missile launches.
Meanwhile the country’s defence minister has confirmed that Seoul now believes it is time to strengthen the country’s military response against North Korea, suggesting the time for talks is now over.
More to follow…