North Korean leader Kim Jong Un in an undated photo released by the North Korean government.

Kcna Kcna / Reuters

A powerful tremor was detected early Sunday in North Korea — a suspected nuclear weapons test — hours after the reclusive regime claimed to have developed a hydrogen bomb.

The US Geological Survey recorded a 6.3 magnitude earthquake at a depth of 0.0 km, a strong indicator the event may have been a nuclear test conducted by Kim Jong Un's military. The USGS described the event as an "explosion."

North Korea has said it detonated a thermonuclear device Sunday, in its sixth and most powerful nuclear test to date, and called it a "perfect success" of "unprecedented" strength.

Minutes after the tremor was detected, South Korea's government said they believed North Korea had conducted a nuclear test, Yonhap News Agency reported.

On Sunday morning, US President Donald Trump tweeted that North Korea was a "rogue nation" and a "great threat and embarrassment."

"North Korea has conducted a major Nuclear Test. Their words and actions continue to be very hostile and dangerous to the United States.......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. 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 last time the North Korean government conducted a nuclear test was nearly a year ago on Sept. 8, 2016, prompting a rebuke from then-president Obama and the United Nation's Security Council. The test also prompted the UN to issue new sanctions on the country.

Sunday's 6.3-magnitude quake suggested whatever weapon was tested was much more powerful than the device tested last year, which produced a 5.3-magnitude tremor.

North Korea also tested a nuclear weapon in January of that year.

The U.S. State Department has not yet commented on the test. South Korea's presidential office said it will hold a National Security Council meeting chaired by President Moon Jae-in and South Korea's military added it had strengthened its monitoring and readiness.

Japan also responded to the test in strong terms. "It is absolutely unacceptable if North Korea did force another nuclear test, and we must protest strongly," Prime Minister Shinzo Abe said.

The test comes during already tense relations with the international community, including the US.

After the North Korean government threatened the US in August, suggesting they were reviewing plans to attack Guam in preparation for possible retaliation against a US attack, President Trump said North Korea would be met with "fire and fury like the world has never seen" if it continued to issue the threats.

Yet North Korea has continued to make aggressive military actions and tests, including firing a missile over Japan just earlier this week.

Just hours after the quake was detected Sunday, North Korea's official news agency KCNA had reported North Korea had developed a new advanced hydrogen bomb, Reuters reported.

The agency reported the new H-bomb could be fitted and would be loaded into an intercontinental ballistic missile, which experts believe would be able to reach the US.

This is a developing story. Check back soon for updates and follow @BuzzFeedNews on Twitter.

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