North Korea launched a rocket at approximately 10:30 p.m. ET, a State Department official told ABC News tonight.
The State Department did not have any information about what kind of rocket, where it went or what kind of payload it might have been capable of carrying.
"The launch by North Korea is seen as a provocative act that will prompt the United States to take appropriate steps to let North Korea know that it can't threaten the safety and security of other countries with impunity," State Department spokesman Fred Lash said.
"North Korea's development, deployment, and proliferation of ballistic missiles, missile related materials, equipment and technology pose a serious threat to the northeast Asian region and to the international community," he said
Lash also said the lauch was a violation of U.N. resolution 1718 and that the United States would seek unspecified "follow-on action at the United Nations" that it will urge other countries to follow.
A South Korean government official told ABC News that the rocket launched was a satellite.
The first stage of the rocket dropped near Akita, Japan, and the second stage dropped in the Pacific Ocean, according to South Korean officials.
Washington has expressed concern that North Korea would use a launch as cover for testing Pyongyang's long-range Taepodong 2 missile, potentially capable of hitting the western United States. North Korea demonstrated its nuclear capability when it tested a crude nuclear weapon in October 2006, and U.S. officials fear a long-range missile could be developed as a delivery vehicle for such a weapon.
For weeks the United States has said a launch would be viewed as a provocative act and would carry consequences. On Friday, President Obama reiterated that warning, saying the United States would pursue "appropriate steps to show North Korea it cannot threaten the safety and stability of other countries with impunity."
American diplomats conveyed the message directly to North Korean officials in recent weeks through their mission to the United Nations in New York, but Defense Secretary Robert Gates admitted last Sunday there were little that could prevent the launch from going forward.
"I would say we're not prepared to do anything about it," said Gates during an appearance on "Fox News Sunday."
The U.S. Navy deployed several ships to the region to track the launch, including one that was capable of shooting the rocket down if necessary.
In an interview with ABC's Martha Raddatz last month, Admiral Timothy Keating, the head of the U.S. military's Pacific Command, which covers North Korea, said the U.S. military would be ready to shoot down the North Korean rocket if ordered to do so.
"We've got Aegis cruisers, we've got radars, we've got space-based systems, we've got ground-based interceptors. We will be fully prepared to respond as the president directs," Keating said.
Japan has deployed missile-defense systems to attempt to shoot down the North Korean missile if it threatens Japanese territory. U.S. diplomats met with key counterparts in recent weeks in a bid to coordinate a response to the launch.
Obama discussed the matter during a meeting with his South Korean counterpart when the two were in London for the G-20 meetings this past week. On March 27, the U.S. envoys for North Korea met with Japanese and South Korean diplomats in Washington to discuss a response.
Japan has said it would like to introduce a resolution in the United Nations Security Council calling for more sanctions on North Korea. It has threatened to impose unilateral sanctions as well.
The Obama administration has refused to speculate in advance how it might respond to the launch, but said only that the matter will be pursued in the UN Security Council.
U.S. officials, speaking on the condition of anonymity, say the United States is prepared to endorse more sanctions on North Korea, but concede that veto-wielding China is unlikely to support such a move.
Washington has been trying to convince North Korea to return to the Six Party Talks, aimed at ridding Pyongyang of its nuclear capability. Negotiations stalled last year in a disagreement over how the other parties would verify the extent of North Korea's nuclear programs.
The United States is also trying to persuade North Korea to release two American journalists detained last month after they allegedly crossed into the totalitarian country from China, where they were interviewing North Korean refugees.
The State Department has said it does not see the journalists' detainment as related to the missile launch and has called for their immediate release. North Korean official media reports say the two will be tried on espionage charges.