Japan remained on alert Wednesday for a North Korean ballistic missile launch expected in the next few days, but Tokyo acknowledged that it was unsure whether Pyongyang would take any action within the day.

Amid growing tensions over North Korea's belligerence, Japan has sent Aegis-equipped Maritime Self-Defense Force destroyers capable of missile interception to the Sea of Japan, while deploying land-based missile-defense systems in the Tokyo metropolitan area.

"We are taking every possible measure to protect Japanese people's lives and safety," Prime Minister Shinzo Abe told reporters in the morning.