SEOUL (AFP, NYTIMES, REUTERS) - North Korea said on Wednesday (Aug 9) that it is considering strikes near US strategic military installations in Guam with its intermediate range ballistic missiles, South Korea's Yonhap news agency reported.

The threat comes days after the US Security Council levied new sanctions on North Korea over its growing nuclear arsenal.

Pyongyang warns that it is ready to stage an all-out war if Washington launches a preventive war against it.

The North's threat came hours after US President Donald Trump warned that any threat by North Korea to the US will be meet with "fire and fury like the world has never seen".

The North's Strategic Force said it's "now carefully examining the operational plan for making an enveloping fire at the areas around Guam with medium-to-long-range strategic ballistic rocket Hwasong-12", according to the official Korean Central News Agency (KCNA) in an English dispatch.

It cited the need to contain the US major military bases on Guam, including the Anderson Air Force Base, where U.S. strategic bombers are based.

The plan will soon be reported to the Supreme Command after "full examination and completion," and will be put into practice "in a multi-concurrent and consecutive way" at Kim Jong Un's order, added the command.

The United States has often dispatched B-1B and other strategic bombers from Guam to South Korea in a show of force. Yonhap news agency reported that two B-1B strategic bombers trained again over South Korea on Tuesday after they were dispatched there late last month following North Korea's second intercontinental ballistic missile (ICBM) test on July 28.

Washington has warned it is ready to use force if need be to stop North Korea's ballistic missile and nuclear programmes but that it prefers global diplomatic action, including sanctions.

"North Korea had best not make any more threats to the United States," said Trump to the camera at his golf course in Bedminster, New Jersey. "They will be met with fire and fury like the world has never seen."

"He has been very threatening beyond a normal state. And as I said they will be met with fire, fury and frankly power the likes of which this world has never seen before."

Trump's stern words to the camera at his golf course in Bedminster, New Jersey, appeared scripted, with him glancing at a paper in front of him, according to the Stars and Stripes website.

Trump's stark comments went well beyond the firm but measured language typically preferred by U.S. presidents in confronting North Korea, and indeed seemed almost to echo the bellicose words used by Kim.

Whether it was mainly a bluff or an authentic expression of intent, it instantly scrambled the diplomatic equation in one of the world's most perilous regions.

Supporters suggested Trump was trying to get Kim's attention in a way that the North Korean would understand, while critics expressed concern that the president could stumble into a war with devastating consequences.

"This is a more dangerous moment than faced by Trump's predecessors," said Mark Dubowitz, chief executive of the Foundation for Defense of Democracies, a nonprofit group in Washington.

"The normal nuanced diplomatic rhetoric coming out of Washington hasn't worked in persuading the Kim regime of American resolve. This language underscores that the most powerful country in the world has its own escalatory and retaliatory options." But Sen. Dianne Feinstein, D-Calif., said it would be counterproductive.

"President Trump is not helping the situation with his bombastic comments," she said in a statement.

The consequences of any US strike would potentially be catastrophic for South Koreans, Japanese and US military personnel within range of North Korean retaliatory strikes.

US military and intelligence officials said any military action against North Korea could unleash a barrage of missiles and artillery in retaliation targeted on Seoul and US bases in South Korea and elsewhere that would likely claim hundreds of thousands of lives.

The UN Security Council unanimously imposed new sanctions on North Korea on Saturday over its continued missile tests, that could slash the reclusive country's US$3 billion (S$4 billion) annual export revenue by a third.

North Korea said the sanctions infringed its sovereignty and it was ready to give Washington a "severe lesson" with its strategic nuclear force in response to any US military action.

North Korea has made no secret of plans to develop a nuclear-tipped missile able to strike the United States and has ignored international calls to halt its nuclear and missile programmes.

North Korea says its ICBMs are a legitimate means of defence against perceived US hostility. It has long accused the United States and South Korea of escalating tensions by conducting military drills.

US stocks closed slightly lower after Trump's comment, while a widely followed measure of stock market anxiety ended at its highest in nearly a month. The US dollar index pared gains and the safe-haven yen strengthened against the US currency.

Retaliatory strike?

US Defence Secretary Jim Mattis has warned of an"effective and overwhelming" response against North Korea if it chose to use nuclear weapons but has said any military solution would be "tragic on an unbelievable scale."

The United States has 28,500 troops in South Korea to guard against the North Korean threat. Japan hosts around 54,000 US military personnel, the US Department of Defence says, and tens of thousands of Americans work in both countries.

Seoul is home to a population of roughly 10 million, within range of massed pre-targeted North Korean rockets and artillery, which would be impossible to destroy by a first US strike.

"There is no question who would prevail in the event of war, regardless of who started it, but there also is no question about the cost," said a former US government expert on Northeast Asia.

On Monday, US Secretary of State Rex Tillerson held the door open for dialogue, saying Washington was willing to talk to Pyongyang if it halted its missile test launches.

Still, he maintained the pressure, urging Thailand on Tuesday for more action against Pyongyang.

The successful testing of two ICBMs last month suggested the reclusive North was making technical progress, Japan's annual Defence White Paper warned.

"Since last year, when it forcibly implemented two nuclear tests and more than 20 ballistic missile launches, the security threats have entered a new stage," its defence ministry said in the 563-page document released on Tuesday.

"It is conceivable that North Korea's nuclear weapons programme has already considerably advanced and it is possible that North Korea has already achieved the miniaturisation of nuclear weapons and has acquired nuclear warheads," it added.

South Korea reiterated further United Nations resolutions against Pyongyang could follow if it did not pull back.

"North Korea should realise if it doesn't stop its... provocations, it will face even stronger pressure and sanctions," Defence Ministry spokesman Moon Sang Gyun told a regular news briefing.

"We warn North Korea not to test or misunderstand the will of the South Korea-U.S. alliance."

Speaking at a regional security forum in Manila on Monday that Tillerson also attended, Chinese Foreign Minister Wang Yi said the new UN resolution showed China and the international community's opposition to North Korea's continued missile tests.

"Owing to China's traditional economic ties with North Korea, it will mainly be China paying the price for implementing the resolution," China's foreign ministry in a statement on Tuesday cited Wang as saying.

"But in order to protect the international non-proliferation system and regional peace and stability, China will, as before, fully and strictly properly implement the entire contents of the relevant resolution."

China, North Korea's lone major ally, has repeatedly said it is committed to enforcing increasingly tough UN resolutions on North Korea, though it has also said what it terms "normal"trade and ordinary North Koreans should not be affected.

The latest UN resolution bans North Korean exports of coal, iron, iron ore, lead, lead ore and seafood. It also prohibits countries from increasing the number of North Korean laborers working abroad, bans new joint ventures with North Korea and any new investment in current joint ventures.