A South Korean rocket appears to have exploded moments after take-off, ending the country's latest attempt to join the space-launch industry.
The Korea Space Launch Vehicle 1 is thought to have blown up 137 seconds after take-off, said science minister Ahn Byong-man.
The rocket lifted off from Goheung's Naro Space Centre at 1701 (0801 GMT).
But contact was lost as the rocket reached an altitude of 70 kilometres (44 miles).
"Looking from the bright flash seen on the camera mounted on the tip of the rocket, it appears [the KSLV-1] exploded in flight during the first-stage ignition," said Mr Ahn.
Pictures on South Korean television appear to show the rocket's final moments, with the cameras following a white speck on its downward trajectory into the sea.
Analysts say the reported failure is a major setback for South Korea in what some observers have described as an "Asian space race".
The launch was South Korea's second attempt to put a satellite in space, after a launch in August 2009 failed.
The country had been hoping to become only the 10th in the world able to put satellites into space, and thereby gain a lucrative slice of the growing space launch industry.
China, India and Japan have developed a launch capability; China has also sent three manned missions into space.
The KSLV-1, built partly in Russia and partly in South Korea, had cost 500 billion won ($400m; £275m).
The satellite - which had been intended to study the effects of climate change - should have separated from the rocket and deployed its solar panels some nine minutes after take-off, at an altitude of 302km.
The rocket had been due to take off on Wednesday, but lift-off was cancelled three hours before launch after fire extinguishing fluids were detected leaking from parts of the equipment.
South Korea's Ministry for Education, Science and Technology said thorough checks had confirmed the leaks did not affect the safety of the rocket and the launch had been rescheduled.
Weather conditions had been closely checked in the final hours before the latest launch. A spokesman for the Korea Aerospace Research Institute (Kari) said all faulty hardware had been replaced and steps taken to prevent a repeat of the earlier faults.
The rocket stood 33m (108ft) tall and was launched from the country's new spaceport on the southern tip of the Korean peninsula.
South Korea's first launch of the two-stage KSLV-1, in August last year, failed to place its satellite payload into the proper orbit.
Four months previously, an attempted space launch by North Korea was deemed to have failed when the US reported that both rocket stages had fallen into the Pacific Ocean.
The North's launch was seen as a cover for a long-range missile test, and prompted UN sanctions.
Pyongyang had voiced irritation at the South's rocket development, but most other powers in the region accepted that its attempt was part of a peaceful civilian programme.