"North Korea's nuclear and ballistic missile programs pose a grave threat to the peace and security of the world and I strongly condemn their reckless action," the president said in a statement in the White House Rose Garden. "North Korea will not find security and respect through threats and illegal weapons."
"We will work with our friends and allies to stand up to this behavior," the president said and pledged to "never waver" from the commitment to protect the American people.
Noting that Russia, China, South Korea and Japan have all condemned North Korea's actions, the president says the country is "inviting stronger international pressure" and as a result, we will "redouble our efforts toward a more robust international non-proliferation regime that all countries have responsibilities to meet."
North Korea's Actions ConfirmedNorth Korea's underground nuclear test and later, reportedly, test-firing the launch of a series of short-range missiles, was confirmed by South Korean officials, citing detection of an artificial earthquake -- magnitude 4.5 -- in Gilju, at the northeastern tip of North Korea.
A few miles away, off the country's east coast, North Korea test-fired three short-range missiles during the day, according to South Korea's Yonhap News agency.
The first short-range missile was fired from Musudan-ri, 300 miles north of Seoul. The second set of two short-range missiles were fired from Wonsan, Kangwon province, only 45 miles north of the North-South border.
President Obama called for global action saying the communist nation is "directly and recklessly challenging the international community." In a statement from Washington, he said, "These actions, while not a surprise given its statements and actions to date, are a matter of grave concern to all nations."
The Chinese foreign ministry also said that it was "resolutely opposed" to the test. Japan placed its own set of sanctions against North Korea three years ago, when the North conducted its previous nuclear test. The ban included imports of North Korean goods and port calls by North Korean vessels. After North Korea launched a long range missile, which North Korea called a communication satellite, last April, the Japanese government extended the duration of the ban by one year.
The U.N. Security Council is expected to hold an emergency meeting today and the U.S. is hoping for swift condemnation of North Korea. But U.S. officials said a push for sanctions against North Korea will depend on the willingness of China and Russia, which hold Security Council vetos.
State Department spokesman Ian Kelly said Secretary of State Hillary Clinton was conferring with her counterparts in Japan, South Korea, China and Russia.
"In her conversations, the secretary stressed the importance of a strong, unified, approach to this threat to international peace and security," Kellys said.
A senior State Department official, speaking on the condition of anonymity, also said that North Korea gave the U.S. an advance warning of less than an hour that it would detonate a nuclear device.
Analysts in Seoul say the North Korean leader Kim Jong Il is trying to mark his country's presence as a full nuclear power.
"North Korea is making a very clear statement that we are a nuclear state. Now deal with us, as such," said Lee Jung-Hoon, professor of international relations at Yonsei University in Seoul. "It's a wake-up call to the international community that we shouldn't pretend as if somehow North Korea would negotiate dismantlement."
Is Another Launch in the Works?
Although it was expected, the timing came as a surprise. U.S. officials did say last week that they were monitoring activity at the nuclear test site but said it was difficult to determine whether a test was imminent given that a lot of that work was underground. Officials also detected activity at the nearby Musudan-Ri, where the long-range Daepodong 2 missile was launched April 5. No missile has been seen there, but the work that's been under way indicates another launch is in the works, according to U.S. officials.
"You can tell that Kim Jong-Il seriously feels that there's not much time left. He'll use whatever means he could to increase the bet," said Choi Jinwook, senior researcher at Korea Institute for National Unification.
"North Korea is a bully. If you concede, it will continue to push, and it's pushing and pushing to the point where now, we can't almost go back," said Lee implying that a harder stance on North Korea is needed to get it to give up the nuclear program. "It's going to be a huge headache, not only for the U.S. but also for the international community as a whole."
ABC News' Luis Martinez and Noriko Namiki contributed to this story.