A Japan Ground Self-Defense Forces type-16 mobile combat vehicle fires during an annual live fire military exercise at the Higashi-Fuji firing range in Gotemba, at the foot of Mount Fuji in Shizuoka prefecture, in this Aug. 26, 2018, file photo. AFP

Japan vowed Monday to bolster its missile deterrence capability to respond to threats by North Korean weapons that are becoming ''more diverse and complex,'' as displayed during Pyongyang's military parade over the weekend.

North Korea, marking the 75th anniversary of its ruling party on Saturday, paraded a variety of weapons systems, unveiling what appeared to be an intercontinental ballistic missile that is larger than any of the North's known ICBMs. It also displayed what was likely an upgraded version of a missile that can be fired from submarines.

While some experts say the weapons could have been mock-ups of missiles under development, the exhibits appear to signify North Korea's continuous upgrading of its weapons capabilities during stalled nuclear diplomacy with the U.S.

''In order to respond to threats that are diversifying and complex, we will firmly work to strengthen our comprehensive missile deterrence capability,'' Chief Cabinet Secretary Katsunobu Kato told a regular news conference Monday. ''We understand that some of those missiles are said to make it difficult for us to respond with our conventional equipment.''