US President Donald Trump led international censure of North Korea's announcement Sunday that it had tested a hydrogen bomb, saying Pyongyang's actions were "very hostile and dangerous to the United States".

Pyongyang's key ally China also expressed strong condemnation, while South Korean President Moon Jae-In called for the "strongest punishment" against the North, including new UN sanctions to "completely isolate" it.

The UN Security Council plans to hold an emergency meeting Monday morning to discuss the international response to the test. UN Secretary-General Antonio Guterres condemned the North Korean test as "profoundly destabilising".

Tensions on the Korean peninsula have spiralled in recent weeks, with North Korea testing an intercontinental ballistic missile (ICBM) and threatening to fire missiles towards the US Pacific island of Guam, which prompted Trump to warn he would rain "fire and fury" on the country.

"North Korea has conducted a major Nuclear Test. Their words and actions continue to be very hostile and dangerous to the United States," Trump tweeted.

Later Sunday, he posted that the US was considering, "in addition to other options, stopping all trade with any country doing business with North Korea."

Such a move could have a big impact on China, a key provider of aid and trade to the North, and which is seen as the only country holding any real influence over its truculent neighbour.

Their relations have become more strained in recent years, however, in part because of Pyongyang's dogged pursuit of its nuclear programme in the face of international condemnation.

- 'Creating serious threat' -

Beijing, which is hosting a summit of the five BRICS nations, said it "expresses resolute opposition and strong condemnation" over Pyongyang's sixth nuclear test, which was felt in Chinese cities hundreds of kilometres from North Korea's borders.

But President Xi Jinping remained silent on the subject at the opening of the BRICS summit in Xiamen, which includes Brazil, India and South Africa.

Later Sunday his Russian counterpart Vladimir Putin said Pyongyang's claim of a successful hydrogen bomb was a threat to regional peace, while urging the international community to respond "in a calm and balanced manner".

The crisis "should be resolved only by political and diplomatic means," he said in a Kremlin statement.

Japanese Prime Minister Shinzo Abe slammed the test as "absolutely unacceptable" and said North Korea's nuclear and missile programmes now pose a more "grave and urgent" threat to his country.

"Whether we can stop North Korea's reckless actions that threaten world peace depends on the cooperation and solidarity of the international community," he added.

- 'New dimension of provocation' -

German Chancellor Angela Merkel and French President Emmanuel Macron urged tougher EU sanctions, saying Pyongyang had "reached a new dimension of provocation".

EU foreign policy chief Federica Mogherini said she was looking forward "to the UN Security Council addressing the matter and taking a firm and effective stand".

Meanwhile British Foreign Secretary Boris Johnson called the test "reckless" but said "none of the military options are good".

"Our message to the Chinese, we think there is more scope for you, the Chinese, to put more economic pressure on the North Koreans," he told Sky News.

NATO secretary general Jens Stoltenberg condemned the test as "yet another flagrant violation" of multiple UN Security Council resolutions.

"NATO is concerned by Pyongyang's destabilising pattern of behaviour, which poses a threat to regional and international security," he said.

Pyongyang, for its part, called the nuclear detonation "a perfect success".

The test was substantially larger than previous ones, generating a 6.3 magnitude earth tremor according to US monitors.

source:AFP