South Korea's first launch of a satellite missed its planned orbit on Tuesday.
Millions of South Koreans watched live telecasts of the KSLV-1 blasting off from a new space centre in the south of the country, television reports said.
However, the research satellite went beyond the orbit planned for it, Science Minister Ahn Byong Man said.
Engineers from the Korean Aerospace Research Institute were trying to locate the satellite, the national news agency Yonhap reported. It was unclear whether radio contact could be made with it.
South Korea would have been the 10th country to launch an artificial satellite into space from its own territory.
Russia was involved in the construction of the rocket, which cost 503 billion won ($402 million).
Earlier this year, North Korea launched a rocket that it said had a satellite on board. Its neighbours and the US said, however, that they detected no satellite in orbit and accused Pyongyang of testing a long-range missile.