Japan's government says it mistakenly sent out a missile alert in parts of the country where there was no need for alarm following North Korea's missile launch on Tuesday morning.

Chief Cabinet Secretary Matsuno Hirokazu told a news conference in the afternoon that the false alert was issued in nine municipalities on Tokyo's Pacific islands through the nationwide J-ALERT emergency warning system.

Matsuno said officials at relevant ministries and agencies are investigating the cause.

He said the government also received reports of the failure of emergency notification systems in four municipalities in the northern prefectures of Hokkaido and Aomori.

Matsuno pledged that government officials will continue to work on providing prompt and precise information to ensure people's safety.