North Korea provokes anger with nuclear test

North Korea claimed it carried out a provocative underground nuclear test today in the escalating international stand-off over its rogue nuclear and missile programmes.

Russia’s defence ministry confirmed an atomic explosion at 9.54am local time (1.54am BST) in north-eastern North Korea, estimating the blast’s yield at 10 to 20 kilotons – comparable to the bombs that flattened Hiroshima and Nagasaki.

The regime also test-fired three short-range, ground-to-air missiles later from the same north-eastern site where it launched a rocket last month, the North Korean news agency reported.

North Korea, incensed by the condemnation of a rocket launch on April 5, warned last month that it would restart its rogue nuclear programme, conduct an atomic test and carry out long-range missile tests.

Today, the country’s official news agency said the regime “successfully conducted one more underground nuclear test on May 25 as part of measures to bolster its nuclear deterrent for self-defence”.

Prime Minister Gordon Brown condemned the test as “erroneous, misguided and a danger to the world. This act will undermine prospects for peace on the Korean peninsula and will do nothing for North Korea’s security,” he said.

“The international community will treat North Korea as a partner if it behaves responsibly. If it does not, then it can expect only renewed isolation.”

US president Barack Obama said a nuclear test would constitute an act of “blatant defiance” of the UN Security Council and a violation of international law, and further isolate North Korea.

North Korea’s claims “are a matter of grave concern to all nations”, he said, calling for international action in a statement from Washington.

“North Korea’s attempts to develop nuclear weapons, as well as its ballistic missile programme, constitute a threat to international peace and security.”

Japanese prime minister Taro Aso said the UN Security Council will meet this afternoon in New York.

He said in Tokyo: “North Korea’s nuclear test poses a grave challenge to nuclear non-proliferation and clearly violates UN Security Council resolutions. We are not tolerating this at all.”

South Korea was grappling with the suicide two days ago of President Lee Myung-bak’s liberal predecessor, Roh Moo-hyun, whose death drew condolences from North Korean leader Kim Jong Il. Kim held a 2007 summit in Pyongyang with Roh, who championed reconciliation with North Korea.

The rise in tensions over North Korea’s nuclear and missile programmes comes amid questions about who will succeed the authoritarian Kim, 67, who is believed to have suffered a stroke last August.

North Korea also has custody of two American journalists – accused of entering the country illegally and engaging in “hostile acts” – who are set to stand trial on June 4.

Today’s atomic test was conducted about 50 miles north west of the northern city of Kilju, Russian defence ministry spokesman Alexander Drobyshevsky said.

Kilju, in the north-eastern province of North Hamgyong, is where North Korea conducted its first nuclear test in October 2006 in a surprise move that angered even traditional ally China and drew wide-ranging sanctions from the UN Security Council.

An emergency siren sounded in the Chinese border city of Yanji, 130 miles to the north west. Residents said they felt the ground tremble.

North Korea boasted that today’s test was conducted “on a new higher level in terms of its explosive power and technology of its control” than in 2006.

Ten to 20 kilotons would be far more than North Korea managed in 2006.

US intelligence officials said the 2006 test measured less than a kiloton – one kiloton is equal to the force produced by 1,000 tons of TNT.

But Russia estimated the force of the 2006 blast at five to 15 kilotons, far higher than other estimates at the time.

Radiation levels in Russia’s Primorye region, which shares a short border with North Korea, were normal today several hours after the blast.

The reported test-firing of short-range missiles took place at the Musudan-ri launch pad on North Korea’s north east coast, some 30 miles from the nuclear test site.

Japan’s coastguard said on Friday that North Korea warned ships to steer clear of waters off the coast near the launch site, suggesting Pyongyang was preparing for a missile test.

South Korean troops were on high alert but there was no sign that North Korean soldiers were massing along the heavily fortified border dividing the two nations.

The two Koreas technically remain at war because their three-year conflict ended in a truce, not a peace treaty, in 1953.

North Korea is believed to have enough weaponised plutonium for at least six atomic bombs, but experts say scientists have not yet mastered the miniaturisation needed to mount a nuclear device on to a long-range missile.