South Korean military on Monday said North Korea fired an unidentified ballistic missile into the sea off South Korea's east coast, the latest in an apparent volley of tests by Pyongyang this year.

"North Korea has fired an unidentified missile into the East Sea," South Korea's Joint Chiefs of Staff said, referring to the body of water also known as the Sea of Japan.

Tokyo also confirmed the launch, with the Japanese defence ministry saying "a suspected ballistic missile was launched from North Korea" in a post on X, formerly Twitter.

Japanese media reported the suspected missile fell outside Japan's Exclusive Economic Zone.

Seoul-based specialist site NK News said the "brief flight time, likely under 10 minutes, pointed to the launch involving a short-range ballistic missile or a multiple launch rocket system."

The latest launch comes after UN sanctions monitoring against the nuclear-armed nation was upended last month by Russia. (AFP)