North Korea fired what appeared to have been an intermediate range ballistic missile on Thursday but it crashed seconds after the test launch, South Korea's defense ministry said, the second such failure this month.
A defense ministry official told Reuters that the launch from near the North Korean east coast city of Wonsan appeared to have been of a Musudan missile with a range of more than 3,000 km (1,800 miles), at about 6:40 a.m. local time (2140 GMT).
Isolated North Korea has conducted a flurry of missile launches and tests of military technology in the run-up to a rare congress of its ruling Workers' Party that is set to begin on May 6.
Thursday's apparent failure, however, marks another setback for young leader Kim Jong Un. A similar missile launched on the April 15 birthday of his grandfather and the country's founder, Kim Il Sung, exploded in what the U.S. Defense Department called a "fiery, catastrophic" failure.
South Korea also says the North is ready to conduct a nuclear test at any time. It would be its fifth nuclear test.
The defense ministry official, who declined to be identified by name, said South Korean and U.S. officials were analyzing the cause of the missile crash, declining to comment on why the launch was revealed hours after it took place.
The South's Yonhap News Agency said the fired missile was not detected by South Korean military radar because it did not fly above a few hundred meters, and was spotted by a U.S. satellite.
The South Korean defense ministry told Reuters it could not confirm that report.
On Saturday, North Korea tested a submarine-launched ballistic missile, which traveled about 30 km (18 miles) off its east coast.