North Korea hails ’successful’ nuclear test

North Korea said it has carried out a successful "nuclear warhead explosion" test to counter what it called US hostility, North Korean state TV reported, angering neighbors and the United States.

An earthquake with a magnitude of 5.3 was detected in the country’s north on Friday morning, South Korea’s meteorological agency said, in what officials said was the biggest ever such blast.

A state TV presenter said: "Scientists ... the DPRK carried out a nuclear explosion test for the judgment of the power of a nuclear warhead newly studied and manufactured by them at the northern nuclear test ground."

The Democratic People’s Republic of Korea is the North’s official name.

"The Central Committee of the Workers’ Party of Korea sent warm congratulations to nuclear scientists ... of the northern nuclear test ground on the successful nuclear warhead explosion test," the presenter said.

The test would also enable the North to produce "as many as it wants a variety of smaller, lighter and diversified nuclear warheads of higher strike power", she said.

The UN nuclear watchdog said the test was in "clear violation of numerous United Nations Security Council resolutions" and disregarded repeated demands from the international community.

"It is a deeply troubling and regrettable act," International Atomic Energy Agency (IAEA) Director General Yukiya Amano said in a video on the IAEA’s website. He added that the IAEA is ready to resume verification activities in North Korea once a political agreement had been reached among the countries concerned.

NATO Secretary General Jens Stoltenberg "strongly condemned" the "very disturbing" development, telling Pyongyang it must drop all nuclear and ballistic missile activities. 

"I strongly condemn these consistent provocations and violations of binding UN Security Council resolutions which undermine regional and international security," he said in a statement.

The tremor, detected by the US Geological Survey and Japan’s Meteorological Agency’s earthquake and tsunami observations division, happened near a known nuclear test site.

In January, North Korea detonated its fourth nuclear device at the same site.