The UN Security Council has condemned North Korea for carrying out a banned long-range rocket launch and warned it could take further action.
The UN's most powerful body held an emergency meeting to discuss the action and said there would be more talks on "an appropriate response".
It said the move violated a 2009 council resolution banning "any launch using ballistic missile technology".
As members headed into the closed Security Council consultations, the US and its European allies including the UK, France and Germany called for the body to deliver "a strong reaction" to the ballistic missile test.
US ambassador to the United Nations, Susan Rice, demanded "consequences" for the rocket launch, adding that North Korea's actions "more than call into question" its commitment to return to talks on its nuclear arsenal.
The blast-off, which had been anticipated, has been viewed with suspicion by critics who believe the country was carrying out a ballistic missile test under cover.
The impoverished state has said it was simply delivering a weather satellite to space and it declared the mission a success.
Experts have said it may take time to confirm that any North Korean satellite is orbiting Earth, but the launch is set to strain tensions in the region.
It tried in April to launch a long-range rocket, but it broke apart shortly after lift-off, crash-landing in the Yellow Sea.
South Korea said the latest attempt - the second under leader Kim Jong-Un - appeared to have broken up in three stages as planned.
South Korea, which is days away from presidential elections, has expressed "grave concern" and its president Lee Myung-Bak immediately called an emergency security meeting, while the UN Security Council is also holding talks.
The White House called it a "highly provocative act that threatens regional security", and China also expressed concern.
British Foreign Secretary William Hague strongly condemned the launch, saying it was a "clear violation" of UN Security Council resolutions.
He said: "I deplore the fact that the DPRK (Democratic People's Republic of Korea) has chosen to prioritise this launch over improving the livelihood of its people."
The rocket was launched shortly before 1am UK time on Wednesday from a site on the northwest coast. Japan's government said it had passed over Okinawa - a trajectory predicted by the North.
Pyongyang announced earlier this month the launch would take place by December 21, later extending the deadline to December 29.
The country is banned from conducting missile and nuclear-related tests under UN sanctions imposed after its 2006 and 2009 nuclear tests.
It is thought to have a handful of rudimentary nuclear bombs, but it is not yet believed to be capable of building warheads small enough to pin on a long-range missile.
Japan, which had been on high alert since the launch window opened, did not try to shoot down the latest rocket, its government said. Tokyo said it believed debris from the rocket had fallen into the sea off the Korean peninsula and the Philippines.
A spokesman for Japan's government called the launch "extremely regrettable", adding: "Our country cannot tolerate this. We strongly protest to North Korea."
American space expert Jonathan McDowell, of the Harvard-Smithsonian Centre for Astrophysics, believes the Unha-3 rocket has indeed delivered a satellite to space.
"Clearly this is much more successful than their last attempt. It's at least as good as they've ever done. They've proved the basic design of it."