North Korea has provoked angry responses from around the world with its announcement that it has tested a nuclear explosive. If the reports are true, Pyongyang has violated a number of international pledges not to build nuclear weapons. Many countries, including the United States, warn Pyongyang may face tough consequences.
The report of the underground blast that has resonated around the world came shortly after 10:30 in the morning Monday, Korean time.
Intelligence advisors told South Korean President Roh Moo-hyun that seismographs had detected a tremor in northeastern North Korea, and that it could be the result of a nuclear test.
Within hours, a North Korean broadcaster read a triumphant announcement.
The announcer says the test produced no radiation leakage, because it was conducted with "wisdom and scientific knowledge." She says the "historic event" brings the army and the North Korean people great pleasure.
The rest of the world was not at all pleased. A lengthy roster of countries began condemning North Korea's actions - led by South Korea, Japan, China and the United States. Others joining in with condemnation include Russia, Britain, France and Australia.
China, North Korea's strongest ally, criticized the reported test in unusually strong language, saying Pyongyang had acted "brazenly." The United States described the test as "a provocative act," and called for United Nations Security Council action as soon as possible.
Security experts in the United States, Japan and South Korea quickly began trying to confirm whether there had indeed been a nuclear test.
President Roh immediately convened a meeting of his top national security officials. Shortly after the meeting, his spokesman, Yoon Tae-young, said that South Korea would react "strictly" to the test, in accordance with Seoul's position that a nuclear-armed North Korea is unacceptable.
Yoon chastises North Korea for reneging on a promise it made a year ago to South Korea, China, Russia, Japan and the United States, to begin dismantling its nuclear weapons programs. Those five nations have worked for three years to convince Pyongyang that living up to its pledges not to build nuclear weapons would produce major diplomatic and economic benefits.
Now, South Korean authorities have halted emergency flood aid shipments to the impoverished North. After a meeting with visiting Japanese Prime Minister Shinzo Abe Monday, President Roh said the apparent nuclear test would "seriously affect" South Korean policy.
Issuing what he calls both "a warning and a prediction," Mr. Roh says it is now very difficult for Seoul to pursue or justify its policy of engagement with North Korea.
South Korean authorities have long said a peaceful and nuclear-free North was the aim of billions of dollars poured into aid and infrastructure projects in the impoverished North.
But Prime Minister Abe described Monday's apparent test as a threat to North Asian security and stability.
Mr. Abe says the world now is living in a new and dangerous nuclear era. He says his government will study taking stern measures against North Korea in coordination with concerned countries and the U.N. Security Council. He says Japan will seek a United Nations resolution, including tough action against North Korea.
As night fell here in downtown Seoul, conservative civic groups began what they say will be two weeks of nightly protests over the North Korean test.
The protesters shout their anger against the Roh Moo-hyun government, for what they describe as policies too indulgent toward Pyongyang. Political analysts say Mr. Roh can look forward to plenty of similar criticism in days to come.