South Korea's president is calling for the "strongest possible" response North Korea’s latest nuclear test.

Moon Jae-in also said on Sunday that he wants United Nations Security Council sanctions to "completely isolate" Pyongyang, according to multiple reports.

North Korean state television said earlier that a test of a miniaturized hydrogen bomb that could fit on an intercontinental ballistic missile (ICBM) was a “perfect success.”

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The South Korean president had earlier called for an emergency meeting of his security council after an artificial earthquake was detected in northern North Korea.

The U.S. Geological Survey on Sunday recorded a 6.3-magnitude earthquake that it described as a "possible explosion" near North Korea's known nuclear test site in the northeast.

The North Korean test ratchets up tensions in the region and represents a show of defiance against President Trump.

Trump last month threatened North Korea with "fire and fury" if it continued to threaten the U.S.

Pyongyang in recent weeks has also conducted four ballistic missile launches.

Trump early Sunday knocked South Korea for its talk of "appeasement" with the North.

"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!" he tweeted.

--This report was updated at 8:05 a.m.