The US defence secretary warned North Korea that any threat to the US or its allies would be met with a “massive military response” on Sunday, as the Trump administration scrambled to respond to Pyongyang’s claim it has tested a powerful hydrogen bomb that can be loaded on to an intercontinental ballistic missile.

“We are not looking to the total annihilation of a country, namely North Korea,” said James Mattis, speaking outside the White House, but “we have many options to do so”.



Trump on attacking North Korea: 'We'll see' – live Read more

He added: “We made clear that we have the ability to defend ourselves and our allies, South Korea and Japan, from any attack. And our commitment among the allies is ironclad: any threat to the United States or its territories, including Guam, or our allies will be met with a massive military response, a response both effective and overwhelming.”

And he told Kim Jong-un to “take heed of the United Nations security council’s unified voice” and de-nuclearise the Korean peninsula. The United Nations security council called a meeting for Monday.

Amid alarm from world leaders over North Korea’s claim that it can now, for the first time, put a nuclear warhead on an ICBM, Trump had earlier upped the ante with a series of provocative statements.

Asked outside church in Washington whether he planned to attack the isolated, hostile dictatorship, the US president replied: “We’ll see.”

He and the first lady were whisked back to the White House from St John’s Episcopal church in an SUV. Shortly afterwards, Trump tweeted: “I will be meeting General Kelly [John Kelly, chief of staff], General Mattis and other military leaders at the White House to discuss North Korea. Thank you.”

Play Video 0:55 North Korea claims successful nuclear test – video report

Earlier in the day, after news emerged overnight that North Korea was believed to have detonated a large hydrogen bomb in a test in the north of the country, deepening the biggest foreign policy challenge faced by his administration, Trump posted a series of tweets.

“North Korea has conducted a major nuclear test,” the president wrote. “Their words and actions continue to be very hostile and dangerous to the United States.”

He added: “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.”

And he also accused South Korea of favouring a policy of “appeasement”, telling Seoul that “will not work” because the North Koreans “only understand one thing!”

Early on Monday, South Korea’s military said its air forces and the army carried out a missile drill in response to North Korea’s nuclear test, adding the drills targeted the area where the test had been carried out.

The military training involved long-range air-to-surface missiles and ballistic missiles, South Korea’s joint chiefs of staff said in a statement. The drill was carried out by only the South Korean military but more are being prepared with the US forces in South Korea, the statement said.

Facebook Twitter Pinterest Donald and Melania Trump visit St John’s Church in Washington on Sunday. Photograph: Pool/Getty Images

Pyongyang said the test, its sixth since 2006, had been a “complete success” and involved a two-stage thermonuclear weapon of unprecedented strength.

There has been no independent verification of North Korea’s claims that it has achieved a key goal in its nuclear programme – the ability to miniaturise a warhead so that it can fit on a long-distance missile.

The regime has earlier released footage of what it said was a hydrogen bomb that would be loaded on to a new ICBM.

Pyongyang’s TV announcement, which was accompanied by patriotic music and images of North Korean landscape and military hardware, said the test had been ordered by the country’s leader, Kim Jong-un.

The explosion caused by a 6.3-magnitude earthquake felt in Yanji, China, about six miles (10km) from North Korea’s Punggye-ri nuclear test site in the north-east of the country.

South Korea’s meteorological administration estimated the blast yield at between 50 to 60 kilotons, or five to six times more powerful than North Korea’s fifth test in September last year.

Kim Young-woo, the head of South Korea’s parliamentary defence committee said later that the yield was as high as 100 kilotons. One kiloton is equivalent to 1,000 tons of TNT.

The previous nuclear blast in North Korea is estimated by experts to have been about 10 kilotons.

Sunday’s test, the first since Trump took office in January, offers further evidence that North Korea is moving perilously close to developing a nuclear warhead capable of being fitted on to an ICBM that can strike the US mainland.

Since it conducted its first nuclear test just over a decade ago, the regime has strived to refine the design and reliability of its weapons, as well as increasing their yield.

Hydrogen bombs are far more powerful than the atomic weapons Pyongyang is believed to have tested so far.

Trump also tweeted again shortly after noon, in apparent support of a new policy initiative announced by his treasury secretary, Steven Mnuchin, earlier in the day, where he called for any countries that trade with North Korea to be barred from trading with the US.

Donald J. Trump (@realDonaldTrump) The United States is considering, in addition to other options, stopping all trade with any country doing business with North Korea.

Mnuchin, also a member of Trump’s national security council, said on Sunday that he wanted to cut off North Korea’s economy because of the test.

“It’s clear that this behavior is completely unacceptable,” he told Fox News. “We have already started with sanctions but I’m going to draft a sanctions package that I’m going to send to the president for his strong consideration, that anybody that wants to do trade or business with them [North Korea] would be prevented from doing trade or business with us. People need to cut off North Korea, economically.”

When asked if the US would take a much tougher stance with Chinese financial institutions and companies in that regard, Mnuchin said: “We are going to strongly consider everything at this point.”

He refused to comment on “classified things” such as whether the test was a hydrogen bomb, not just an atomic bomb, and whether the US believed that North Korea had now miniaturized its nuclear capability to the point where it could put a nuclear warhead on an ICBM.

“I can only say that the intelligence community has been doing an amazing job,” he said.

He said he had spoken to Trump about the issue that morning, but refused to clarify what the president meant when he said North Korea only understood “one thing”, or comment on the prospect of military action.

“The president has made it clear this is not the time for just talk, this is the time for action,” Mnuchin said. “Our objective will continue to be to de-nuclearize the peninsula … He will consider everything but we are not going to broadcast our actions. My focus right now is on additional economic sanctions. China has a lot of trade with them; there is a lot we can do to cut them off economically.”

China’s foreign ministry earlier said in a statement: “The Democratic People’s Republic of Korea has once again conducted a nuclear test in spite of widespread opposition from the international community. The Chinese government resolutely opposes and strongly condemns it.”

Before taking office, Trump declared North Korea would not be allowed to develop an ICBM capable of reaching the US mainland under his presidency.

After Pyongyang carried out two successful ICBM tests in July, Trump warned it would face “fire and fury like the world has never seen” if it made any further threats.

North Korea has since threatened to fire a salvo of missiles into the seas around the US Pacific territory of Guam, and fired a ballistic missile over Japanese territory for the first time, ending US hopes that Trump’s threats had cowed Pyongyang into a pause in missile tests and a possible opening for talks.

Complicating matters, Trump seems to be considering asking aides to prepare for US withdrawal from a free trade agreement with South Korea, it was reported on Saturday. Mnuchin stressed that “no decision has been made”.

Jeff Flake, a member of the Senate foreign relations committee, said: “I do not think that that would be good in any circumstances; it’s particularly troubling right now.”



North Korea nuclear test: what we know so far Read more

Asked about Trump’s tweeted response to the nuclear test, Flake told CNN: “I have good confidence in our national security team and those who are advising the president. He does not have experience in this kind of situation. I’m confident that the people around the president are giving him good advice and he will take it - I sure hope he does.”

The Republican senator added: “I’ve had my concerns about statements from the president about Nato and foreign policy. We want someone who is measured and sober and consistent. Allies want to have that and our enemies need to have that.”

Flake said that Trump’s notorious threat last month to meet North Korean aggression with “fire and fury” had not been not advisable.

“We have not slowed the advance of their nuclear program, but harsh rhetoric does not either,” he said. “Just about nothing we have done so far has slowed it down. It becomes a cliche to say there are no good options here, but there really are not. For those who believe we can simply strike and knock out their capability, they do not understand the situation there. But all options need to be on the table.”