North Korea has launched a long-range rocket, which critics say is a test of banned missile technology.
But according to local media, North Korea had successfully placed a satellite in orbit.
The launch was condemned by Japan, South Korea and the US, who have requested an emergency meeting of the UN Security Council on February 7.
South Korea says it is to begin discussing with the US the deployment of a missile defense system.
Ryu Je-Seung, a senior defense official, said if the THAAD missile system – considered one of the most advanced in the world – were deployed it would be only to counter the threat from the North.
In a statement, the North Korean National Aerospace Development Administration said earth observation satellite Kwangmyongsong-4 had entered orbit about 10 minutes after lift-off from the Sohae space centre in North Phyongan province.
Announcing the launch on state TV, a newsreader said it had been ordered by North Korea’s leader Kim Jong-un and said the country planned to launch more satellites in the future.
South Korean Defense Ministry spokesman Moon Sang Gyun said a warship had detected the launch at 09:31.
The rocket launch was roundly condemned by the international community. US Secretary of State John Kerry called it a “flagrant violation” of UN resolutions and warned of “significant measures to hold the DPRK [North Korea] to account.”
China said it “regrets” North Korea’s actions but urged “the relevant parties” to “refrain from taking actions that may further escalate tensions on the Korean peninsula”.
Contenders for the Republican ticket in the US presidential election this year were asked for their reaction during a debate in New Hampshire.
Donald Trump said China was the key.
“I would get on with China. Let China solve that problem.”
UN Security Council resolutions ban North Korea from carrying out any nuclear or ballistic missile tests.
South Korean analysts had speculated that North Korea might carry out the launch ahead of February 16, the birthday of the late North Korean dictator Kim Jong-il.