SEOUL/WASHINGTON-- North Korea said Sunday that it has successfully conducted a test of a hydrogen bomb that can fit on its intercontinental ballistic missile (ICBM) in its sixth and most powerful nuclear detonation yet.

In an "important" announcement carried by its state television, Pyongyang said the test was conducted at 12:00 p.m. (Pyongyang Time) under the direction of leader Kim Jong-un. It called the test a "perfect" success.

The announcement came hours after an artificial earthquake with a 5.7 magnitude was detected near North Korea's nuclear site in the northeastern area, according to Seoul's meteorological service.

"The H-bomb test was carried out to examine and confirm the accuracy and credibility of the power control technology, and internal structural design newly introduced into manufacturing the H-bomb to be placed as the payload of the ICBM," the North's official Korean Central News Agency said.

Earlier in the day, North Korea claimed that it has developed a hydrogen bomb that can be mounted on an ICBM.

The sixth nuclear explosion since 2006 came amid heightened tensions after North Korea tested two ICBMs in July. Analysts said the ICBM tests could put much of the U.S. mainland within range, including Los Angeles and Chicago.

In January 2016, North Korea conducted its fourth nuclear test, which Pyongyang claimed to be a test of a hydrogen bomb. Outside experts said that it appeared to be a test of a boosted fission weapon, rather than an H-bomb.

South Korea's weather agency said Sunday that the latest blast was five to six times more powerful that the North's fifth test in September 2016. The explosion a year ago, presumably with a yield of 10 kilotons, triggered a 5.04 magnitude earthquake.

Sunday's test was 11 times more destructive than its fourth test, it said.

"(The success) also marked a very significant occasion in attaining the final goal of completing the state nuclear force," the KCNA said.

It has not been verified whether the wayward regime actually detonated a hydrogen bomb. But the latest test seemed to bring North Korea a step closer to the goal of developing a nuclear-tipped ICBM capable of reaching the continental U.S.

Along with the miniaturization of a nuke weapon, obtaining atmospheric re-entry technology is a key element in developing an ICBM, which analysts said the North may be a few years from achieving.

"The sixth nuke test indicates that North Korea is pushing for dealing with the U.S. on equal footing after securing a nuclear power status," said Yang Moo-jin, a professor at the University of North Korean Studies.

South Korea strongly condemned North Korea for its test, with its leader Moon Jae-in ordering the pursuit of the most powerful sanctions on North Korea with the international community.

The U.N. Security Council agreed to hold an emergency meeting Monday to discuss its response.

Pyongyang is already under multiple sets of U.N. sanctions for its nuke tests and missile launches, the latest have been adopted last month.

In Washington, U.S. Defense Secretary Jim Mattis warned North Korea of a "massive military response" should the country threaten the U.S. or its allies.

Speaking outside the White House after meeting with U.S. President Donald Trump and the national security team, he made clear that the U.S. has the ability to defend itself and its allies, South Korea and Japan, from any attack.

"Any threat to the United States or its territories, including Guam, or our allies will be met with a massive military response, a response both effective and overwhelming," he said, with the chairman of the U.S. Joint Chiefs of Staff, Gen. Joe Dunford, at his side.

The international community does not seek the "total annihilation" of North Korea, he added, but "we have many options to do so."

In a series of tweets, Trump called North Korea a "rogue" nation whose words and actions continue to be "very hostile and dangerous" to the U.S.

Indicating a policy rift with Seoul, he went on to say, "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!"

Trump also threatened to cut off all trade with countries that do business with North Korea, an apparent warning to China, which is responsible for 90 percent of the North's trade.

When asked by a reporter whether he plans to attack the North, Trump answered, "We'll see."

Tensions have already flared up between the U.S. and the North after the ICBM tests with Trump earlier warning of "fire and fury" against the North.

Pyongyang threatened to fire a salvo of missiles into waters near the U.S. territory of Guam though it held off on the plan later.

The U.S. offered a conciliatory gesture toward the North, saying that North Korea's brief restraint from provocative acts could pave the way for dialogue.

But the unruly regime responded with the firing of an intermediate-range ballistic missile over Japan last week.

The international community is expected to tighten the screw on the North with tougher sanctions and pressure. China, the North's main ally and trading partner, would be under further pressure to do more in reining in North Korea.

President Moon is expected to be dealt a heavy blow in his push for rapprochement with Pyongyang. He is seeking a dual-track approach of dialogue and sanctions in resolving North Korea's nuclear issue.

He earlier said that North Korea would be crossing a "red line" if it weaponizes a nuclear-tipped ICBM.

Source: Yonhap News Agency