North Korea defied weeks of international warnings against a planned satellite launch as it fired a long-range rocket on Friday, a South Korean official told the Yonhap news agency.
The Unha-3 rocket blasted off at 7:39 am time (2239 GMT Thursday) from the Tongchang-ri launch site, South Korean Defence Ministry spokesman Kim Min-seook said, dpa reported.
"South Korean and US intelligence authorities believe that North Korea's missile launch ended in failure," he said.
North Korea had said it intended to launch an Earth observation satellite into orbit during a five-day window that started Thursday, to commemorate the centenary on Sunday of the birth of founder Kim Il Sung.
The international community had expressed fears that a launch could be a cover for a ballistic missile test, violating UN resolutions prohibiting Pyongyang from engaging in ballistic missile and nuclear activity.
South Korean President Lee Myung-bak called an emergency meeting of security staff Friday morning, Yonhap reported, citing officials.
Hours earlier, US Secretary of state Hillary Rodham Clinton announced that the Group of Eight countries meeting Thursday in Washington had agreed "to be prepared to take additional steps" if North Korea went ahead with the threatened launch. Further UN action would be pursued if the launch went through, she said.
In 2006, the UN Security Council unanimously imposed commercial sanctions and banned North Korea from importing ballistic missile technology in response to a nuclear test that year. The council in 2009 unanimously adopted stricter sanctions, including interception of North Korean ships, after Pyongyang exploded another nuclear device.