United States Defense Secretary James Mattis has laid out plainly US military options against North Korea's threats in a short statement outside the White House on Sunday (3 August).

Mattis said threats to the US, its territories or its allies "will be met with a massive military response", adding that it would be "a response both effective and overwhelming".

Mattis also named Guam when mentioning the US overseas territories - a Pacific island that North Korea has previously threatened with attacks.

The strong words from the defence secretary came after North Korea said they had successfully tested a hydrogen bomb that could be fitted to an intercontinental ballistic missile.

If true, it could mean that the country now has capabilities to launch a nuclear warhead at the continental United States.

Mattis said that the US does not seek the "total annihilation" of North Korea but that "we have many options to do so".

US President Donald Trump and Treasury Secretary Steve Mnuchin said earlier on Sunday that the country was looking into new sanctions that would mean countries doing business with North Korea could no longer do any business with the United States.

"The United States is considering, in addition to other options, stopping all trade with any country doing business with North Korea," Trump tweeted on Sunday.

In an earlier tweet, he branded North Korea "a rogue nation".

"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," the president tweeted.

The nuclear test is the latest provocation from North Korea and an escalation from a number of missile tests that it had undertaken in the last few months. It is the country's sixth nuclear test.