North Korea fired an "unspecified" ballistic missile toward the East Sea on Monday, the South Korean military said.
It comes three days after Pyongyang launched cruise missiles into the Yellow Sea.
The South Korean military did not provide further details as "an analysis is currently underway," Seoul-based Yonhap News reported.
Confirming the development, Japan said the missile did not cause any damage, Tokyo-based Kyodo News reported.
The shot marks North Korea's first ballistic missile launch since it test-fired a new intermediate-range ballistic missile tipped with a hypersonic warhead.
Pyongyang said it conducted a "super-large warhead" power test for a strategic cruise missile and test-fired a new anti-aircraft missile in the Yellow Sea on Friday.
