Japanese PM Sanae Takaichi told reporters that the missile apparently fell outside Japan's exclusive economic zone, with no damage to planes or ships reported, Kyodo news agency said.
North Korea launched a ballistic missile toward the Sea of Japan, according to the South Korean military on Monday, according to a report by Kyodo News.
The US Indo-Pacific Command in statement said it was aware of Pyongyang's "ballistic missile launches and are consulting closely" with South Korea and Japan, as well as other regional allies and partners.
Korean Central News Agency report made no mention of the second missile. It also did not elaborate on the nature of the simulated warhead, like where the missile launched from and where it landed.
The firing comes as North Korea had pledged to launch a rocket carrying a military reconnaissance satellite again "as soon as possible" following a failed launch in May.
North Korea on Wednesday fired an apparent ballistic missile into the East Sea, Yonhap news agency reported citing the South Korean Joint Chiefs of Staff (JCS).
Moments before a US aircraft carrier staged joint drills with South Korea in waters south of Jeju Island, Pyongyang fired two short-range ballistic missiles (SRBMs) toward the East Sea on Monday, Yonhap News Agency reported.