A live-fire exercise simulating an attack on North Korea’s nuclear test site was carried out to “strongly warn” Pyongyang over its claimed test of a hydrogen bomb, Seoul’s Joint Chiefs of Staff have said.
The drill involved F-15 fighter jets and South Korea’s land-based “Hyunmoo“ ballistic missiles, and the released live weapons “accurately struck” a target in the sea off the country’s eastern coast, the JCS said.
It came after Kim Jong Un’s regime on Sunday claimed “perfect success” in an underground test of what it called a hydrogen bomb.
It was the North’s sixth nuclear test since 2006 and involved a device potentially vastly more powerful than a nuclear bomb.
US defence secretary Jim Mattis hit back, saying the US will answer any threat from the North with a “massive military response – a response both effective and overwhelming”.
Earlier, President Donald Trump threatened to halt all trade with countries doing business with the North, a veiled warning to China, and faulted South Korea for its “talk of appeasement.”
The tough talk from America’s commander in chief and the retired general he picked to oversee the Pentagon came as the Trump administration searched for a response to the escalating crisis.
Mr Trump, asked by a reporter during a trip to church if he would attack the North, said: “We’ll see.”
No US military action appeared imminent, and the immediate focus appeared to be on ratcheting up economic penalties, which have had little effect so far.
The UN Security Council scheduled an emergency meeting at the request of the US, Japan, France, Britain and South Korea.
It would be the Security Council’s second urgent session in under a week on the North’s weapons tests, which have continued in the face of a series of sanctions.
Members of the US Congress expressed alarm at the North’s test and emphasised strengthening US missile defences. Leaders in Russia, China and Europe issued condemnations.
Mr Mattis told reporters that America does not seek the “total annihilation“ of the North, but then added: “We have many options to do so.”
The administration has emphasised its pursuit of diplomatic solutions, knowing the potentially horrific costs of war with the North.
But the decision to have Mr Mattis deliver a public statement seemed to suggest an escalating crisis.
The precise strength of the underground nuclear explosion had yet to be determined. South Korea’s weather agency said the artificial earthquake caused by the explosion was five times to six times stronger than tremors generated by the North’s previous five tests.
North Korea’s state-run television broadcast a special bulletin to announce the test, and said Mr Kim attended a meeting of the ruling party’s presidium and signed the go-ahead order.
Earlier, the party’s newspaper published photos of him examining what it said was a nuclear warhead being fitted onto an intercontinental ballistic missile.
Sunday’s detonation builds on recent North Korean advances that include test launches in July of two ICBMs that are believed to be capable of reaching the mainland US.
The North says its missile development is part of a defensive effort to build a viable nuclear deterrent that can target US cities.
North Korea’s accelerating push to field a nuclear weapon that can target all of the US is creating political complications for Washington as seeks to reassure allies that it will uphold its decades-long commitment to deter nuclear attack on South Korea and Japan.
That is why some questioned Mr Trump’s when he tweeted that Seoul is finding that its “talk of appeasement” will not work.
He added the North Koreans “only understand one thing,” implying military force might be required.
Mr Trump also suggested putting more pressure on China, the North’s patron for many decades and a vital US trading partner, in the hope of persuading Beijing to exert more effective leverage on its neighbour.
The president tweeted that the US is considering “stopping all trade with any country doing business with North Korea”.
That would be radical as the US imports about 40 billion US dollars (£31 billion) in goods a month from China, North Korea’s main commercial partner.
US secretary of state Rex Tillerson was calling counterparts in Asia, but it is unclear what kind of sanctions might make a difference.
Lassina Zerbo, head of the UN test ban treaty organisation, said sanctions already imposed against North Korea are not working.