The United Nations Security Council held an emergency session Tuesday morning in response to North Korea's latest nuclear test.
Britain's deputy ambassador to the U.N., Philip Parham, says his government hopes the council will send a message of clear condemnation. But he says it is not clear what further action the council will take.
North Korea already is under strong U.N. economic sanctions because of its nuclear and missile programs. Pyongyang defied international warnings to carry out its third nuclear test Tuesday.
Pyongyang said the "successful" test was in response to what it called the "reckless hostility" of the United States, which has led the global charge to expand sanctions against the communist state.
Following the test, North Korea's Foreign Ministry warned of unspecified additional measures. South Korea has already placed its military on alert because of the possibility of additional North Korean nuclear tests or missile launches.
The Comprehensive Test Ban Treaty Organization said the test "constitutes a clear threat" to world peace. The multilateral organization says its preliminary data indicate the explosive power was twice as large as that seen in North Korea's 2009 nuclear test.
The South Korean Defense Ministry says the explosion generated 6 to 7 kilotons of power.
In the United States, Leon Panetta, the departing secretary of defense, said the U.S. must be ready to deal with Pyongyang and other rogue states.
"We're going to have to deal with weapons of mass destruction and their proliferation," he said. "We're going to have to continue to deal with rogue states like Iran and North Korea. We just saw what North Korea has done in these last few weeks. A missile test and now a nuclear test. They represent a serious threat to the United States of America and we've got to be prepared to deal with that."
The test brought quick world condemnation, with U.N. Secretary-General Ban Ki-moon calling it "deeply destabilizing."
Just hours after the test, Japanese Defense Minister Itsunori Onodera told VOA correspondent Steve Herman that Tokyo will need to boost its defenses in response to the North Korean provocation.
"Because North Korea has conducted such a provocative action we need to bolster our countrys defense system to face this kind of threat. But due to our [pacifist] constitution, our country is in a very restricted situation when it comes to having nuclear weapons as well as increasing our [conventional] forces. Therefore it is very important to strengthen the U.S.-Japan security alliance," he said.
South Korea on Tuesday said it will quickly deploy missiles capable of striking anywhere in North Korea to protect itself.
North Korea for weeks had threatened to carry out its third nuclear test in retaliation for United Nations sanctions that were expanded following Pyongyang's December long-range rocket launch.
State media said the underground test used a lighter, smaller nuclear bomb with greater explosive force than previous tests - raising fears Pyongyang has achieved a breakthrough in creating a bomb small enough to place on a missile.
Security analyst Michael McKinley with the Australian National University said in an interview with VOA that it is important to determine in the coming days whether North Korea used plutonium or highly-enriched uranium to conduct the test.
"The crucial evidence here will be whether they used plutonium as they did in the other two [nuclear tests], or whether they've used uranium in this one. That would represent of course that they've got a secret uranium enrichment program," he said.
In 2009, Pyongyang announced it would begin enriching uranium, to give it a second fuel for nuclear weapons. Experts say uranium-enrichment programs are more sustainable and easier to hide in secret facilities.
too well to be on some suicide mission. Kim Jong Ill was the largest single customer for the company that produces Hennessy.
