The Latest on North Korea's nuclear test and the world reaction (all times local):
South Korea says the U.S. military will soon install additional missile-defense launchers at the site in southeastern South Korea in order to counter North Korea's provocations.
South Korea's defense ministry says the installation of four missile launchers of the Terminal High Altitude Area Defense system, also known as THAAD, was a "temporary" deployment as it needed to respond to the advancement of the North's nuclear and missile threats.
The ministry says the final deployment of the THAAD missile system will hinge on an environmental impact study. The U.S. anti-missile system has been a source of diplomatic tensions between South Korea and China, which fears its powerful radar may peer into Chinese territory. It has also faced opposition from local residents who say the previous administration made a hasty decision to install the U.S. anti-missile system without due procedures.
China and other major emerging economies say they "strongly deplore" North Korea's latest nuclear test.
The leaders of Brazil, Russia, India, China and South Africa are meeting at the BRICS summit in southeastern China. The leaders adopted a declaration Monday in which they expressed "deep concern over the ongoing tension and prolonged nuclear issue on the Korean peninsula."
The text of the declaration, posted on India's Ministry of External Affairs website, also said the countries emphasized the issue should be settled through peaceful means and dialogue — echoing Beijing's long-held position.
Japan's leader says he will seek to bolster his country's missile defense in the face of the growing North Korean threat.
Prime Minister Shinzo Abe said Monday that his government would push for adding equipment such as the U.S.-developed Aegis Ashore missile interceptor.
His comments to a meeting of top officials from the government and his ruling party came one day after North Korea conducted its biggest nuclear test to date.
Abe said Japan would maintain high caution for what he called "further provocations" from North Korea.
Japan's Defense Ministry said last week in its 2018 budget proposal that it is considering the Aegis Ashore anti-missile system.
Egypt has condemned North Korea's nuclear test, warning of threats to regional security.
The Foreign Ministry expressed worries Monday that the escalating activity could unleash a nuclear arms race in the region.
The statement on Monday comes nearly 10 days after the U.S. announced it was withholding millions of dollars in aid to Egypt over human rights concerns. Observers, however, have noted that the move is also linked to Egypt's relations with North Korea as the U.S. continues to isolate North Korea economically and politically.
In a phone call in July, President Donald Trump gave a thinly veiled warning to Egypt's President Abdel-Fattah el-Sissi to stop its economic cooperation with Pyongyang.
A publication of the ruling Communist Party has urged China to avoid imposing a full embargo on North Korea. The Global Times newspaper said in an editorial Monday that such a response would trigger war.
The paper said the nuclear test conducted Sunday was "another wrong choice that Pyongyang has made" in violation of U.N. Security Council resolutions.
It said China should avoid overly aggressive sanctions, as long as North Korea's tests do not contaminate China's northeastern provinces. China's Ministry of Environmental Protection says radiation monitoring data showed no impact from the test as of early Monday.
Meanwhile, leading Chinese government-backed scholar Lu Chao says China will likely agree to slap more sanctions on its ally North Korea over its latest nuclear test. But Lu asserted that dialogue remained necessary.
"The U.S should take specific and sincere actions toward North Korea instead of making enhanced threats," said Lu, of the Academy of Social Sciences in Liaoning province abutting North Korea.
South Korean media says Seoul's military believes North Korea is readying the launch of a ballistic missile, possibly an ICBM.
Yonhap news agency reports that Seoul's defense ministry also measures North Korea's nuclear test at 50 kilotons. The detonation Sunday was the strongest ever from the North, which claimed the test was of a hydrogen bomb.
South Korea responded to the nuclear test with live-fire drills off its eastern coast Monday that were meant to simulate an attack on the North's main nuclear test site.
The leaders of South Korea and Japan have agreed to work together to build support for further sanctions against North Korea following its latest nuclear test.
Japanese broadcaster NHK says Japanese Prime Minister Shinzo Abe and South Korean President Moon Jae-in discussed the crisis by telephone Monday, ahead of an emergency U.N. Security Council meeting.
Abe also spoke with President Donald Trump and Russian leader Vladimir Putin late Sunday night.
Japan's Foreign Ministry said that Abe strongly encouraged Russia to respond constructively as a permanent member of the Security Council. He and Putin agreed to continue talks later this week in Vladivostok, Russia.
Abe told Trump that North Korea's nuclear test is a serious threat to Japan's security that poses a "head-on challenge" to the international community.
Australian Prime Minister Malcolm Turnbull has called on China to bring North Korea to its "senses" following its apparent test of a hydrogen bomb.
He said China will be enforcing U.N. economic sanctions against North Korea but "there will be more that needs to be done given the affront that North Korea has shown to China" by testing its sixth nuclear device on Sunday.
Turnbull told reporters in Canberra on Monday that the risk of war breaking out on the Korean Peninsula is at its highest in over 60 years. He said China, as the North's closest ally and commercial partner, had the economic leverage to and therefore the responsibility to influence North Korea.
South Korea's military says it conducted a live-fire exercise simulating an attack on North Korea's nuclear test site to "strongly warn" Pyongyang over the latest nuclear test.
Seoul's Joint Chiefs of Staff says the drill involved F-15 fighter jets and the country's land-based "Hyunmoo" ballistic missiles and that the released live weapons "accurately struck" a target in the sea off the country's eastern coast.
The JCS says that the target was set considering the distance to where the North's test site was and the exercise was aimed at practicing precision strikes and cutting off reinforcements.
The U.N. Security Council has scheduled an emergency meeting after North Korea conducted its most powerful nuclear test to date.
The U.S., Japan, France, Britain and South Korea requested Monday's meeting after North Korea detonated what it called a hydrogen bomb.
It will be the Security Council's second urgent session in under a week on the North's weapons tests, which have continued in the face of a series of sanctions.
After North Korea launched a ballistic missile over Japan, the council Tuesday strongly condemned the test and reiterated demands that Pyongyang halt its ballistic missile and nuclear weapons programs.
Monday could bring additional condemnation and discussion of other potential steps.
Meanwhile, U.N. Secretary-General Antonio Guterres condemned Sunday's nuclear test. His spokesman calls it "profoundly destabilizing for regional security."
U.S. Defense Secretary Jim Mattis is responding to North Korea's latest nuclear test by saying threats to the United States and its allies "will be met with a massive military response."
Mattis spoke at the White House on Sunday following a meeting with President Donald Trump and national security advisers. He says any response will be "both effective and overwhelming."
Mattis says the United States is "not looking to the total annihilation" of North Korea, but added "we have many options to do so."
North Korea claimed "perfect success" in an underground test of what it called a hydrogen bomb — potentially vastly more destructive than an atomic bomb. It was the North's sixth nuclear test since 2006, but the first since Trump took office in January.
The president of the European Commission says North Korea's latest nuclear test compels the international community to unite in swift and decisive reaction.
Donald Tusk said the European Union stands ready to sharpen its policy of sanctions and invites North Korea to restart dialogue on its nuclear and missile programs without condition.
In Sunday's statement, Tusk said the EU calls on the U.N. Security Council "to adopt further U.N. sanctions and show stronger resolve to achieve a peaceful denuclearization of the Korean peninsula," adding, "The stakes are getting too high."
He said North Korea must abandon its nuclear weapons of mass destruction and ballistic missile programs in a verifiable and irreversible manner and it must cease all related activities at once.
Turkey has strongly condemned the latest North Korean nuclear test.
In a statement published Sunday, Turkey's foreign ministry said the test was "irresponsible and provocative," while ignoring international law and endangering regional peace and security.
Turkish troops were part of a United Nations command aiding South Korea during the Korean War between 1950 and 1953. More than 700 soldiers died in the battles.
President Donald Trump says the United States is considering halting trade with "any country doing business with North Korea."
Trump said on Twitter Sunday that the approach was under consideration, "in addition to other options," after North Korea detonated a thermonuclear device in its sixth and most powerful nuclear test.
Treasury Secretary Steven Mnuchin said Sunday that he was putting together new sanctions seeking to cut off trade with North Korea. On "Fox News Sunday," Mnuchin described Pyongyang's behavior as "completely unacceptable."
Trump is meeting with his national security team Sunday afternoon to discuss North Korea.
The president was asked if he would attack North Korea as he left a church service Sunday. He said: "We'll see."
Russian President Vladimir Putin has spoken by telephone with Japanese leader Shinzo Abe and urged restraint in responding to North Korea's claim to have set off a hydrogen bomb test.
Putin, in China for a meeting of leaders of the BRICS economic bloc, called Abe on Sunday.
Kremlin spokesman Dmitry Peskov told journalists that Putin "said the international community could not give in to emotions, should act calmly and deliberately, and stressed that the complex settlement of the nuclear and other problems of the Korean Peninsula can be achieved exclusively through political and diplomatic means."
North Korea has claimed a "perfect success" for its most powerful nuclear test so far, a further step in the development of weapons capable of striking anywhere in the United States.
U.S. President Donald Trump, asked if he would attack the North, said, "We'll see."
The president was meeting later Sunday with his national security team. North Korea's nuclear test was the first since Trump took office in January.
In a series of tweets, Trump said the latest provocation from the isolated communist country reinforces the danger facing America. He said "talk of appeasement" is pointless because "They only understand one thing!"
After attending church in Washington, the president made his "We'll see" comment in response to a question from reporters.