North Korea sharply raised the stakes Sunday in its standoff with the rest of the world, detonating a powerful nuclear device that it claimed was a hydrogen bomb that could be attached to a missile capable of reaching the mainland United States.

Even if Kim Jong Un’s regime is exaggerating its feats, scientific evidence showed that North Korea had crossed an important threshold and had detonated a nuclear device that was vastly more powerful than its last — and almost seven times the size of the bomb that destroyed Hiroshima.

Tensions had already been running high, with Kim repeatedly defying international condemnation and increasingly blunt warnings by President Trump, and continuing to launch ballistic missiles.

But Sunday’s blast — North Korea’s sixth nuclear test but the first since Trump took office — could escalate those tensions to a new level.

Trump sharply condemned the test, saying North Korea is “very hostile and dangerous to the United States.”In a pair of tweets issued Sunday morning, Trump wrote: “North Korea has conducted a major Nuclear Test. Their words and actions continue to be very hostile and dangerous to the United States … North Korea is a rogue nation which has become a great threat and embarrassment to China, which is trying to help but with little success.”

Trump also delivered an admonishment of sorts to South Korea, saying that “appeasement with North Korea will not work” and suggesting that more severe steps must be taken to influence Kim’s regime.

China said Sunday that it “resolutely opposes and strongly condemns” the launch, adding to denunciations from South Korea and Japan.

The nuclear device that North Korea tested appeared to be so large that Vipin Narang, an expert on nuclear proliferation and strategy at the Massachusetts Institute of Technology, called it a “city buster.”

“Now, with even relatively inaccurate intercontinental ballistic missile technology, they can destroy the better part of a city with this yield,” Narang said.

The nuclear test took place at exactly noon local time at North Korea’s Punggye-ri testing site and was recorded as a 6.3-magnitude earthquake, according to the U.S. Geological Survey. It was followed eight minutes later by a 4.1-magnitude earthquake that appeared to be a tunnel collapsing at the site.

Japan immediately sent up sniffer planes to try to measure radiation levels.

North Korean state media said the test was carried to determine “the accuracy and credibility” of its “H-bomb to be placed at the payload of the ICBM.” North Korea tested its intercontinental ballistic missile for the first time in July, and its second test later that month showed that the rocket could theoretically reach Denver or Chicago. Continue reading.