On Sunday, North Korea said it had detonated a thermonuclear device, making it the sixth and most powerful test the country has ever launched. It described the launch as “perfect success.” This marks a significant step toward its ultimate aim of building nuclear weapons that could reach the continental United States. However, South Korea and Japan have condemned the blast.

Though the accuracy and strength of the blast are yet to be determined, Seoul’s meteorological agency said the artificial earthquake the blast caused was six times powerful than the tremors that resulted from previous tests Pyongyang had conducted.

The blast was reported to have shook buildings in Russia and China.

The latest nuclear test

CNN reported that the Nuclear Test was carried out at exactly 12:29 p.m. local time. It was conducted at the Punggyi-ri Test Site where Pyongyang has carried out most of its nuclear tests in the past. South Korean Officials put the magnitude around 5.7, while the United States Geological Survey said the magnitude was around 6.3. The most powerful artificial quake from previous blasts was at 5.3 magnitudes.

On Sunday afternoon, North Korea’s state-run KCNA media in a special broadcast announced the test. The statement said leader Kim Jong Un had signed the go ahead order after attending a meeting of the ruling party.

Earlier on Sunday, the ruling party’s newspaper published an article on its front page showing images of Kim examining what it described as a nuclear warhead being topped on the nose of a missile.

Condemnation from neighbors

The test on Sunday builds on recent Pyongyang’s nuclear advances including the two intercontinental ballistic missiles (ICBM) launched in July that is believed to be able to reach the US mainland.

North Korea argues that its missile and nuclear weapons program are solely for targeting US cities, territories and allies to counter what it called American aggression.

In a statement, Chinese foreign ministry condemned the latest test and urged Pyongyang to stop its erroneous actions that continue to escalate tensions. However, the South Korean National Security Council held an emergency meeting chaired by President Moon Jae-in and released a statement that Moon will adopt all available measures, including the deployment more military assets from the US or pressing for an expanded UN Security Council sanctions against North Korea.

Japanese Prime Minister Shinzo Abe described the blast as absolutely unacceptable.