Lee Mi-Seon, a director of the National Earthquake and Volcano Center, shows a map of a North Korean location during a briefing about the 'artificial earthquake' in North Korea, at the Korea Meteorological Administration in Seoul on Sept. 3, 2017. Getty Images

North Korea announced early Sunday that it has successfully test fired a hydrogen bomb, eliciting alarmed reactions from world leaders. This was Pyongyang's sixth nuclear test, and according to experts ten times more powerful than earlier tests conducted over the years.

An H-bomb, also known as a thermonuclear bomb, is a weapon energized by the nuclear fusion of hydrogen isotopes — deuterium and tritium. The bomb produces a much stronger blast, nearly hundred times more destructive than an atomic bomb, which relies on tearing heavy atoms such as plutonium and uranium apart — a process known as fission.

Even in H-bombs, the primary explosion needed to generate the energy that helps kick-start the fusion process is caused by a fission reaction, which later causes a secondary explosion, which is triggered by the fusion of the hydrogen isotopes.

Two atomic bombs were used to level Hiroshima and Nagasaki during World War II that killed more than 200,000 people.

On Sunday, South Korea's Kim Young-woo of the minor opposition Bareun Party said that the explosive power of the latest nuke apparently appeared to be much stronger than Pyongyang's fifth one estimated to have a yield of 10 kilotons. One kiloton is equivalent to 1,000 tons of TNT.

“(The North’s latest test) is estimated to have a yield of up to 100 kilotons, though it is a provisional report,” Kim Young-woo told Yonhap News Agency over the phone. “The test will be a very crucial political and strategic inflexion point.”

The bombs dropped by the United States over Hiroshima and Nagasaki, which killed over 200,000 people, had yields of 13 and 21 kilotons, respectively.

Fusion-powered H-bombs can have yields measurable in megatons. The most powerful nuclear weapon ever detonated was the H-bomb “Tsar Bomba,” which was tested by the Soviet Union in 1961 and had a yield of at least 50 megatons, making it 3,800 times more powerful than the Hiroshima bomb. The bomb is 100 megatons and reportedly has a fireball radius of 1.88 miles and a radiation radius of 4.65 miles. To date, H-bombs have never been used in war.

While announcing Sunday's test, North Korea said its sixth nuclear test was a "perfect success." The confirmation came just hours after seismologists detected an earth tremor measuring 6.3-magnitude.

The test took place in Kilju County, where the North's Punggye-ri nuclear test site is situated. The "artificial quake" was 9.8 times more powerful than the tremor from the North's fifth test, Japan's state weather agency said.

Chinese authorities said two tremors were felt in a gap of few minutes, some are suspecting a tunnel collapse where the underground nuclear test was conducted. Concerns also grew about a radiation leak.

North Korea's state TV also said Sunday that the H-bomb can be mounted on an Intercontinental Ballistic Missile (ICBM).

“Our hydrogen fuel, which can be arbitrarily adjusted from tens to hundreds of kilotons depending on the target of the nuclear strike, not only exerts enormous destructive power,” but can also explode at a high altitude, producing a “super powerful EMP [electromagnetic pulse] against a vast region,” North Korea's KCNA said.

Following the test, South Korea’s Joint Chiefs of Staff said in a statement that the country's military has "raised its alert status and stepped up its surveillance on North Korea."

This is not the first time North Korea has claimed to have tested an H-bomb. Last year in January, Pyongyang claimed to have tested an H-bomb, eliciting alarmed reactions from world leaders.

North Korea has carried out nuclear bomb tests since at least 2006 and has been subject to United Nations sanctions. Most recently, President Donald Trump threatened Kim Jong Un with "fire and fury" if they did not stop their nuclear advancements.

It is now believed Trump's rhetoric did little to stop the reclusive country from continuing its nuclear prowess. The United States is yet to release a statement about North Korea's nuclear test and it is unclear how the Trump administration will react.