North Korea said Sunday that it successfully conducted a test of a hydrogen bomb meant to be loaded onto an intercontinental ballistic missile (ICBM).
The announcement was made on state-run television. A news reader called the test a "complete success" and said the "two-stage thermonuclear weapon" had "unprecedented" strength. North Korea's leader Kim Jong Un ordered the test, according to the announcement.
It is the rogue nation's sixth, and most powerful, nuclear test.
President Trump responded on Twitter, commenting on North Korea's continuing "hostile and dangerous" actions toward the U.S. and its being a "great threat and embarrassment to China."
North Korea's announcement of the test came a few hours after a 6.3-magnitude "explosion" was detected at 12:29 p.m. local time in North Korea, according to the United States Geological Survey (USGS) announced Sunday.
According to the USGS, the seismic activity occurred 24 kilometers east northeast of Sungjibaegam, North Korea. "Possible explosion, located near the site where North Korea has detonated nuclear explosions in the past," read a statement on the USGS website, before confirmation that it was indeed a nuclear test.
The USGS said that a second, 4.1-magnitude seismic event occurred 22 kilometers east northeast of Sungjibaegam. "Seismic event collocated with the larger possible explosion 8 minutes and 32 seconds earlier," read a statement on USGS's website. "This significantly smaller event is likely a secondary feature (possibly a structural collapse) associated with the larger event."
U.S. National Security Adviser H.R. McMaster spoke with his South Korean counterpart, Chung Eui-yong of the country's National Security Office, for 20 minutes in an emergency phone call following the test, according to the South Korean presidential office.
Eui-yong said Sunday that President Moon Jae-in will seek every available diplomatic measure, including new sanctions from the United Nations Security Council. He said Moon will also discuss with the Trump administration ways to deploy the "strongest strategic assets" the U.S. has.
Speaking at a press conference Sunday at the South Korean Ministry of Defense, Cho Han-kyu, the director general of operations with the Joint Chiefs of Staff, said the military "strongly condemns North Korea in conducting ICBM-level missile launches and nuclear tests, even stronger than those conducted in the past, regardless of our government's suggestions to ease military tension and bring peace to the Korean peninsula."
Han-kyu added, "the South Korea-U.S. alliance, in closest cooperation ever, has all the capability to punish North Korea and we will show our action demonstrating a strong response of the South Korea-U.S. combined forces (against North Korea)."
Condemnation of the test came from China, Russia and France, as well.
China's Ministry of Foreign Affairs said in a statement, "The Democratic People's Republic of Korea has once again conducted a nuclear test in spite of widespread opposition from the international community. The Chinese government resolutely opposes and strongly condemns it."
The Russian Foreign Ministry said in a statement Sunday that North Korea's nuclear test "deserves absolute condemnation," adding that immediate dialogue and negotiations are necessary. It says that's the only way settle the Korean Peninsula's problems, "including the nuclear problem."
The statement continued, "This yet another example of Pyongyang’s outright disregard of the demands of respective UN Security Council resolutions and international law deserves absolute condemnation."
The ministry said Russia is willing to participate in negotiations, "including in the context of the implementing of the Russian-Chinese road map."
French President Emmanuel Macron said in a statement he "calls on the members of the United Nations Security Council to quickly react to this new violation by North Korea of international law."
Macron continues, "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 program."
South Korea's weather agency, the Korea Meteorological Administration, said on Sunday that the apparent nuclear test appears to have been several times stronger than its previous test.
The agency estimated that the nuclear blast yield of the presumed test was between 50 to 60 kilotons, or five to six times stronger than the North Korea's fifth test, conducted in September 2016.
Prior to North Korea's announcement, Japan confirmed that the rogue nation conducted a nuclear test. "It is absolutely unacceptable if North Korea did force another nuclear test, and we must protest strongly," Prime Minister Shinzo Abe said.
And South Korea's Joint Chiefs of Staff had also "presumed" that North Korea did indeed conduct a sixth nuclear test, before its neighbor to the north made the announcement. When news first broke of the seismic activity, South Korea's Joint Chiefs of Staff said the seismic activity was artificial.
South Korea's presidential office said it will hold a National Security Council meeting chaired by President Moon Jae-in.
The North Korean government released photos earlier Sunday of Kim Jong Un talking with his lieutenants as he watched a silver, peanut-shaped device that was apparently the purported thermonuclear weapon destined for an ICBM. What appeared to be the nose cone of a missile could also be seen near the alleged bomb in one picture. The photo could not be independently verified. Another photo showed a diagram on the wall of a bomb mounted inside a cone.
ABC News' Christopher Donato, Michael O'Keefe, Dragana Jovanovic and Joohee Cho contributed to this report.