North Korea fired an unspecified ballistic missile off its east coast, South Korea's Joint Chiefs of Staff said in a statement on Wednesday, a launch also reported by Japan's military.

The missile was still flying, according to a Japanese Defence Ministry official quoted by broadcaster NHK. No further details were immediately available about the launch, which came barely a month after North Korea's last launch and is its twelfth such launch this year.

The launch also comes after North Korea made heated complaints in recent days over U.S. military activities, accusing American spy planes of violating airspace in its economic zones and condemning a recent visit to South Korea by an American nuclear-powered cruise missile submarine. This year North Korea has test fired its first ever solid-fuel intercontinental ballistic missile (ICBM), and conducted a failed attempt to launch its first-ever spy satellite on a new launch vehicle. United Nations Security Council resolutions ban North Korea's use of ballistic missile technology, including for satellite launches.

The Security Council, as well as a number of nations, have imposed sanction on North Korea for its missile and nuclear weapons programmes. Analysts say commercial satellite imagery shows North Korea is expected to stage displays of military force, including a large parade, for an upcoming holiday on July 27 that commemorates its claim to victory in the 1950-1953 Korean War against the United States, South Korea, and their allies.