The CNN television channel said the missile had traveled hundreds of miles before plunging into the Sea of Japan.
But an unnamed US official told the broadcaster later that the missile had disintegrated over land after flying approximately 20 miles and did not reach the sea.
South Korea’s Joint Chiefs of Staff reportedly said it was launched from a location north of Pyongyang at around 5:30 a.m local time (20:30GMT). The initial assessment is that the launch failed.
"It is estimated to have failed," the South Korean military said, as quoted by the national news agency Yonhap.
The military said it was analyzing launch data.