(c) 2009, Los Angeles Times
SEOUL, South Korea -- North Korea announced Monday that it had completed an underground nuclear test, as the Asian regime continues attempts to bolter its nuclear capabilities after a recent rocket test launch.
The nation's official Korean Central News Agency reported that the test was completed Monday, raising alarm on the Korea Peninsula and across the region.
Analysts in recent days had predicted that North Korea would attempt a second rocket or nuclear test. The reclusive nation had threatened to do so unless the United Nations apologized for imposing sanctions after North Korea's missile test in April.
North Korea also test-fired a short-range missile, according to South Korea's Yonhap news agency. South Korea's military said it was checking the report.
About 10 a.m., seismologists from the U.S., South Korea and Japan reported earthquakes in a northeastern area, just a few miles from where North Korea conducted a nuclear test in 2006, according to wire reports.
The U.S. Geological Survey recorded a 4.7 tremor in the northeast, about 40 miles northwest of Kimchaek.
A State Department official said that the United States was aware of the North Korean report.
"We are consulting with our allies," the official said. "Once we have established the facts, we will have more to say."
Japanese officials, meanwhile, said they would respond to North Korea's nuclear test "in a responsible fashion" at the United Nations, said a foreign ministry spokesman attending a regional meeting in Vietnam.
In Seoul, where markets tumbled at news of the nuclear test, South Korean President Lee Myung-bak called for an emergency session of the country's security ministers. The ministers were meeting in the underground bunker of the Blue House, the South Korean White House.
According to the North Korean news agency's release, "The test will contribute to defending the sovereignty of the country and the nation and socialism and ensuring peace and security on the Korean Peninsula and the region around it."
The release added that the test was successful and was more powerful than its previous test.
"The current nuclear test was safely conducted on a new higher level in terms of its explosive power and technology," the news agency report said. "The results of the test helped satisfactorily settle the scientific and technological problems arising in further increasing the power of nuclear weapons and steadily developing nuclear technology."
In April, North Korea announced that it had begun harvesting plutonium from spent fuel rods at its main nuclear plant. The move, in defiance of U.N. sanctions, came as another blow to international efforts to dismantle the communist nation's nuclear program.
North Korea is thought to have enough weaponized plutonium to make more than half a dozen bombs, analysts say.
Russia, China, South Korea, Japan and the U.S. have been negotiating with North Korea on ending its nuclear weaponry program for years, but the rogue nation recently walked away from the so-called six-party talks.
North Korea had been angered by international reaction to what it called a peaceful satellite launch April 5, which many observers believed was actually a long-range missile test.
Security experts on Monday said they were awaiting the results of the strength of the North's latest nuclear test.
Daniel Pinkston, Northeast Asia Deputy Project Director for the International Crisis Group, a global security think tank, said that the previous North Korean nuclear test registered at about 1-kiloton, a measure of the amount of the explosives involved.
Most tests by other nations have ranged from 20 to 40 kilotons, Pinkston said.
"We're waiting to see what the yield (or strength) of the latest test was," he said. "Apparently, the North Koreans had suggested to the Chinese that its test would be in the 4-kiloton range."
The 2006 test was considered a failure by many analysts and North Korea might be trying to work out design flaws in its current test, he added.
"This test was pretty predictable. North Korea has been ready for this event and told the whole world about it," Koh Yu-hwan, a Dongguk University professor of North Korea studies, said Monday.
He said that North Korean leader Kim Jong Il has been frustrated by a lack of progress with desired one-on-one talks with the Obama administration.
"For the moment, it seems that North Korea internally agreed to strengthen its nuclear deterrence," he said.
Analysts said the nuclear test was the latest move in Kim's strategy to boost his position at home. Kim, who many believe suffered a debilitating stroke last year, is said to be trying to secure support for one of his three sons to succeed him.
A successful nuclear program would defy the global community and win support for his chosen successor from the nation's hard-line military forces, said to number more than 1 million men.
Staff writer Paul Richter in Washington and researcher Ju-min Park in Seoul contributed to this report.