US President Barack Obama said on Monday that North Korea's nuclear and missile tests were a "matter of grave concern to all nations" and warranted action by the international community.
Obama, in a statement after Pyongyang conducted a nuclear test and reportedly fired a short-range missile, said, "North Korea is directly and recklessly challenging the international community. North Korea's behavior increases tensions and undermines stability in Northeast Asia."
The nuclear test was Pyongyang's second -- its first was in October 2006 -- and came just two months after North Korea launched a rocket believed to be a test of its long-range missile capability. Pyongyang said it had put a communications satellite into space.
"North Korea's attempts to develop nuclear weapons, as well as its ballistic missile program, constitute a threat to international peace and security," said Obama, adding that Washington would work through the UN Security Council and the six-party talks on North Korea to address the issue.
"North Korea's attempts to develop nuclear weapons, as well as its ballistic missile program, constitute a threat to international peace and security," he said.
A US State Department official said earlier the United States was still analyzing data from the test. The (US) Geological Survey confirmed that a seismic event took place consistent with a test, the official said on condition of anonymity.
"We are consulting with our six-party and UN Security Council partners on next steps," the official added. Under the so-called "six-party" talks among the two Koreas, China, Japan, Russia and the United States, North Korea committed in 2005 to abandon all its nuclear programs.
North Korea said it successfully conducted a nuclear test on Monday, a move certain to further isolate the prickly state, which argues it has no choice but to build an atomic arsenal to protect itself in a hostile world.
The latest test follows years of on-off negotiations with regional powers, which have been pressing the impoverished state to give up its nuclear ambitions in return for massive aid and an end to the country's pariah status.