North Korea attempted to launch a missile early Tuesday, South Korea's military said.
"We assume North Korea failed firing a missile this morning," from its east coast, a Defence Ministry spokesman in Seoul said.
The rocket type had not been identified, but could be a Musudan intermediate-range ballistic missile, the South's Yonhap News Agency cited unnamed sources as saying.
The isolated Pyongyang regime suffered three failed Musudan launches in April, it said.
Tensions on the peninsula are high, after North Korea held an atomic test explosion in January, and launched a long-range ballistic missile in February, prompting a tightening of international sanctions.