North Korea fired at least three ballistic missiles Thursday, prompting an alert in Japan that one may have flown over its territory.

It was uncertain whether the missiles actually passed over Japan but the launches follow a record single-day barrage from Kim Jong Un’s regime, one that included the first ballistic missile it has shot across a nautical border with South Korea.

North Korea started this week by threatening to take “powerful measures” if the US doesn’t halt military drills with partners including South Korea, in what might be an effort by Kim to lay the groundwork for his first nuclear test in five years.

Japan urged its residents in northeastern regions to take cover Thursday morning, after Tokyo said a missile flew over the country’s territory into the Pacific Ocean. South Korea’s military had earlier reported the launch, with the Yonhap News Agency saying the rocket appeared to be a longer-range system.

North Korea fired at least 23 ballistic missiles on Wednesday — its largest-ever such demonstration of military might — after protesting US and South Korean military exercises. The allies have said they believe Kim Jong Un is preparing to conduct his first nuclear test in five years.

Washington, Tokyo and Seoul have promised a coordinated response if Pyongyang sets off an atomic device, which — like ballistic missile launches — would be a violation of United Nations Security Council resolutions.

North Korea had previously fired a ballistic missile over Japan last month, the first such test since 2017. – BLOOMBERG