North Korea Says It Conducted Hydrogen Bomb Test

North Korean leader Kim Jong-Un delivers his New Year's speech on Jan. 1. The country announced late Tuesday that it had tested a hydrogen bomb.

Jung Yeon-je/AFP/Getty Images

North Korea announced on state television that it tested its first hydrogen bomb. The announcement followed a magnitude 5.1 earthquake that shook near the rogue nation's nuclear test site, Pyunggye-ri at 10 a.m. local time.

The hydrogen bomb test was "an act of self defense" against foreign threats, the announcement from the North said. "We've joined the rank of nations with nuclear weapons. We won't use the nuclear weapon as long as there's no invasion of our autonomy."

If verified, this would be North Korea's first nuclear test since 2013. It has staged two previous tests before that. Analysts that study satellite imagery had reported tunnel activity at the Pyunggyre-ri test site as recently as last month.

The nature of the bomb has not yet been confirmed independently, and international experts were skeptical in December when North Korea announced it had created a hydrogen bomb.

A hydrogen bomb is an advanced kind of nuclear weapon that creates most of its explosive power through the fusion of hydrogen atoms. Hydrogen weapons (also called thermonuclear weapons) are much more powerful than "standard" nuclear bombs made of uranium or plutonium. Only a few countries are known for sure to have hydrogen bombs: the United States, Russia, the United Kingdom, France and China.

Regardless of the nature of the test, if confirmed it could strain North Korea's relations with China, its closest ally. In September the Chinese foreign minister urged the Pyongyang government not to do anything that could increase regional tensions.