The dust has yet to settle on the reported hydrogen bomb test conducted by North Korea before US President Donald Trump rounded on his country's ally, South Korea, saying Seoul was now in favour of a policy of appeasement regarding Pyongyang.
On Saturday morning the North Koreans set off an underground explosion that registered over 6 on the Richter scale, and later a smaller explosion was also listed but nuclear experts suggest it was a tunnel collapsing at the site.
North Korea has promised to continue with its nuclear missile programme in spite of UN sanctions, and China has been accused by the US of assisting North Korea by continuing to trade with the pariah state.
Trump tweeted on his official account that the American faced a difficult situation.
"North Korea has conducted a major Nuclear Test. Their words and actions continue to be very hostile and dangerous to the United States."
But he saved his most aggressive tweets for South Korea's leader, President Moon Jae-in.
"South Korea is finding, as I have told them, that their talk of appeasement with North Korea will not work, they only understand one thing!" he tweeted.
He also suggested that China was embarrassed by the actions. But aviation watchers say its clear Beijing was aware that there was some major incident planned as they ordered their airlines to fly around North Korean airspace before the nuclear test.
There have been a number of reported incidents involving airlines and North Korean missile tests, including one in 2014 where a Chinese airline narrowly avoided being struck, and another on July 28 when Pyongyang fired a missile over Japanese airspace. In that incident, the Air France flight 293 had flown past the area where the missile exploded ten minutes before, according to the Pentagon.
In the 2014 incident, a China Southern Airlines jet carrying 220 passengers passed through the line of the North Korean missile a few minutes after it was fired. That was reported by a South Korean official at the time, although Beijing refused to confirm the incident.
Here is North Korea's entire statement concerning the bomb test.
"Pyongyang, September 3 (KCNA) -- The Nuclear Weapons Institute of the DPRK gave the following statement in connection with the perfect success in the test of a hydrogen bomb for ICBM:
Scientists in the nuclear field of the DPRK successfully carried out a test of H-bomb for ICBM in the northern nuclear test ground of the DPRK at 12:00 on September 3, true to the Workers' Party of Korea's plan for building a strategic nuclear force.
The H-bomb test was carried out to examine and confirm the accuracy and credibility of the power control technology and internal structural design newly introduced into manufacturing H-bomb to be placed at the payload of the ICBM.
The result of the experimental measurements showed that the power specifications of nuclear warhead, including total explosion power and fission to fusion power rate and all other physical specifications reflecting the qualitative level of two-stage thermo-nuclear weapon fully complied with design figures. It was also confirmed that even though the recent test was carried out with the bomb of unprecedentedly big power, there were neither emission through ground surface nor leakage of radioactive materials nor did it have any adverse impact on the surrounding ecological environment.
The test re-confirmed the precision of the compression technology of the first system of the H-bomb and the fission chain reaction start control technology and proved once again that the nuclear material utility rate in the first system and the second system reached the levels reflected in the design.
Symmetrical compression of nuclear charge, its fission detonation and high-temperature nuclear fusion ignition, and the ensuing rapidly boosting fission-fusion reactions, which are key technologies for enhancing the nuclear fusion power of the second-system of the H-bomb, were confirmed to have been realized on a high level. This helped prove that the directional combination structure and multi-layer radiation explosion-proof structural design of the first system and the second system used for the manufacture of the H-bomb were very accurate and the light thermal radiation-resisting materials and neutron-resisting materials were rationally selected.
The test helped draw the conclusion that the Korean-style analytic method and calculation programs for the complicated physical processes occurring in the first and second systems were put on the high level and that the engineering structure of the H-bomb as a nuclear warhead designed on the Juche basis including the structure of the nuclear charge of the second system was creditable.
The test once again confirmed the reliability of the concentration-type nuke detonation control system fully verified through a nuclear warhead detonation test and test-launches of various ballistic rockets.
The perfect success in the test of the H-bomb for ICBM clearly proved that the Juche-based nukes of the DPRK have been put on a highly precise basis, the creditability of the operation of the nuclear warhead is fully guaranteed and the design and production technology of nuclear weapons of the DPRK has been put on a high level to adjust its destructive power in consideration of the targets and purposes. It also marked a very significant occasion in attaining the final goal of completing the state nuclear force.
The Central Committee the WPK extended warm congratulations to the scientists and technicians in the nuclear field in the northern nuclear test ground on their successful H-bomb test for ICBM."
