Last updated 00:25, September 4 2017
North Korea's "words and actions continue to be very hostile and dangerous to the United States", US President Donald Trump tweeted after North Korea's latest nuclear test.
US President Donald Trump has called North Korea "an embarrassment" after the rogue nation confirmed it had successfully tested a hydrogen bomb meant for an intercontinental ballistic missile.
The move on Sunday by North Korea is a direct challenge to Trump, who hours earlier had talked by phone with Japanese Prime Minister Shinzo Abe about the "escalating" nuclear crisis in the region.
Trump has sent several strongly-worded tweets condemning North Korea's actions:
Russian President Vladimir Putin warned before the tes that Kim Jong Un and Donald Trump were on the verge of "a large-scale conflict".
Donald J. Trump
North Korea has conducted a major Nuclear Test. Their words and actions continue to be very hostile and dangerous to the United States.....
US President Donald Trump has labelled North Korea "an embarrassment".
Donald J. Trump
..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.
Donald J. Trump
South Korea is finding, as I have told them, that their talk of appeasement with North Korea will not work, they only understand one thing!
The hydrogen bomb test ordered by leader Kim Jong Un was a "perfect success" and was a "meaningful" step in completing the country's nuclear weapons programme, North Korean state television said.
North Korea says it has carried out its sixth nuclear test, this time using a newly built hydrogen bomb. The blast is the most powerful to date and caused a significant earthquake.
China's Foreign Ministry on Sunday urged North Korea to stop its "wrong" actions, after Pyongyang said it successfully tested an advanced hydrogen bomb.
Leaders around the world have condemned North Korea's actions.
New Zealand's Foreign Affairs Minister Gerry Brownlee said in a statement the test was "a highly dangerous affront to the entire international community".
A pedestrian in Japan watches a monitor showing an image of North Korean leader Kim Jong-Un in a news programme reporting on North Korea's sixth nuclear test.
"North Korea has again demonstrated its complete disregard for its obligations under United Nations Security Council resolutions, and for international norms against nuclear testing," Brownlee said.
"North Korea has a choice. It can continue on this path, inviting further pressure and isolation and entrenching poverty and misery for its own people. Or it can choose membership of the international community and the security and prosperity that comes with it. Only North Korea can make this decision."
French President Emmanuel Macron said: "The international community must treat this new provocation with the utmost firmness, in order to bring North Korea to come back unconditionally to the path of dialogue and to proceed to the complete, verifiable and irreversible dismantling of its nuclear and ballistic programme."
The Russian foreign ministry released a statement saying: "In the emerging conditions it is absolutely essential to keep cool, refrain from any actions that could lead to a further escalation of tensions". It added that North Korea risked "serious consequences".
Japanese Prime Minister Shinzo Abe said North Korea's "nuclear and missile development programmes pose a new level of a grave and immediate threat" and "seriously undermines the peace and security of the region".
South Korean President Moon Jae-in said North Korea's sixth nuclear test should be met with the "strongest possible" response, including new United Nations Security Council sanctions to "completely isolate" the country.
Australia has condemned North Korea's "flagrant defiance" of UN Security Council resolutions and urged the world body to take further action against the "dangerous pariah regime".
"We call for the UN Security Council to urgently consider further strong measures that would place pressure on North Korea to change course," Australian Prime Minister Malcolm Turnbull said in a joint statement with Foreign Minister Julie Bishop.
Australia called for all countries, especially the five UN veto powers "to apply the maximum possible pressure to this dangerous pariah regime", according to the statement.
The International Atomic Energy Agency, which has no access to North Korea, called the nuclear test "an extremely regrettable act" that is "in complete disregard of the repeated demands of the international community".