North Korea today revealed it had detonated a hydrogen bomb, triggering a 5.1-magnitude earthquake and propelling the dictatorship on a new collision course with world powers.

The thermonuclear weapon is believed to have detonated into the atmosphere at 10am local time at the Punggye-ri test site in the north-east of the country, with tremors felt many miles away.

Footage was aired on state television that purported to be of the explosion, showing a thick, black mushroom cloud rising high into the air.

Before North Korea’s announcement, a magnitude 5.1 earthquake was measured in the country near the site of an earlier nuclear weapons test, officials said Tuesday night. The tremblor was detected about 12 miles ENE of Sungjibaegam and the South Korean weather agency said indications were that it was “artificial.”

“We have perfectly succeeded in testing our first hydrogen bomb,” an anchor said on North Korean state TV. “It was one hundred percent capable from our own wisdom, technology, and power. We have now scientifically test-proved a miniaturized hydrogen bomb.”

The announcement by North Korea was swiftly criticised by world leaders with South Korea calling it “a grave provocation to our national security”. South Korea’s vice foreign minister, Lim Sung-nam, said during an emergency meeting that North Korea’s “provocation is in clear violation of Security Council resolutions and a serious challenge to international peace and security.”

China plans to summon North Korea’s ambassador in Beijing to the Foreign Ministry to lodge a strong protest, spokeswoman Hua Chunying told reporters at a daily briefing Wednesday.

Japanese Prime Minister Shinzo Abe condemned the alleged test, saying it was a “serious threat” to Japan’s security and “clearly violates the UNSC resolution and is a serious challenge to the nuclear non-proliferation efforts.”

The U.N. Security Council will meet Wednesday morning in New York for a closed-door session to discuss North Korea’s claim that it tested a hydrogen bomb, diplomats have told CNN.