The United States warned it could launch a "massive military response" to any threats from North Korea following Pyongyang's provocative detonation of what it claimed was a miniaturized hydrogen bomb.

Defense Secretary Jim Mattis spoke out on Sunday after North Korea carried out an unexpectedly strong nuclear test, more powerful than the bomb that levelled Hiroshima in 1945.

President Donald Trump called an emergency meeting of his national security advisers and had his second telephone call of the weekend with Japanese Prime Minister Shinzo Abe, but did not talk to South Korea's Moon Jae-In -- instead accusing Seoul of "appeasement".

He threatened drastic economic sanctions, including "stopping all trade with any country doing business with North Korea."

US monitors measured a powerful 6.3-magnitude earthquake near the North's main testing site on Sunday, felt in parts of China and Russia, with an aftershock possibly caused by a rock collapse.

The North -- which in July carried out two intercontinental ballistic missile (ICBM) launches that apparently brought much of the US mainland into range -- hailed its test of what it described as a hydrogen bomb designed for a rocket as "a perfect success."

Mattis told reporters: "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.

"We are not looking to the total annihilation of a country, namely North Korea," he added, but warned: "We have many options to do so."

The White House said the US was committed to "defending our homeland, territories, and allies using the full range of diplomatic, conventional, and nuclear capabilities at our disposal."

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