SEOUL: North Korea on Monday tested a nuclear bomb many times more powerful than its first in 2006, angering enemies and allies alike and prompting UN Security Council members to call an emergency session.

The hardline communist state, which stunned the world with its first atomic bomb test in October 2006, made good on its threat to stage another test after the Security Council censured it for an April rocket launch.

The North “successfully conducted one more underground nuclear test on May 25 as part of the measures to bolster up its nuclear deterrent for self-defence in every way,” the official Korean Central News Agency (KCNA) said.

“The current nuclear test was safely conducted on a new higher level in terms of its explosive power and technology,” it said.

The foreign ministry in China, the North’s most important ally, said it was “resolutely opposed” to the test.

“China strongly demands that North Korea keeps its promise of denuclearisation and ceases all actions that could further worsen the situation,” it said a statement.

Russia’s foreign ministry said the test threatened regional stability, violated the Security Council’s will and impeded non-proliferation efforts. China and Russia — both part of a six-nation forum working to persuade the North to give up its nuclear programmes — had in the past resisted efforts at the UN to punish the North harshly over its nuclear activities. The force of today’s blast was between 10 and 20 kilotons, according to Russia’s defence ministry, vastly more than the estimated one-kiloton blast three years ago.

Japan’s Meteorological Agency said that based on recorded seismic activity, the energy level of the test was four times bigger than the last one.

Baek Seung-Joo of the Korea Institute for Defence Analyses told AFP that if rough estimates by some private analysts are right, “the power of the second blast is comparable to the bombs which hit Hiroshima and Nagasaki.”

The Security Council, which sanctioned the North for its previous test, planned to meet this afternoon in New York.

The North also test-fired three short-range missiles today, South Korea’s military said.

“North Korea’s attempts to develop nuclear weapons, as well as its ballistic missile programme, constitute a threat to international peace and security,” US President Barack Obama said in a statement.

“The danger posed by North Korea’s threatening activities warrants action by the international community. “By acting in blatant defiance of the United Nations Security Council, North Korea is directly and recklessly challenging the

international community,” Obama said. The North informed the US and China in advance of the test, a South Korean official said.