Japan's government says it has not changed its view that North Korea launched a new type of ICBM-class ballistic missile last Thursday.

Chief Cabinet Secretary Matsuno Hirokazu told reporters on Monday that the view is based on comprehensive analysis of the data, including the missile's flight altitude.

Matsuno was responding to a question about South Korean media reports that the US and South Korean authorities had concluded that the missile was of the Hwasong-15 type launched in 2017. Pyongyang said it was the Hwasong-17, a new type of ICBM.

Matsuno said a simple calculation shows the missile's maximum range could exceed 15,000 kilometers, a level quite different from those launched by the North in the past.

He said the launches remain a grave threat to the peace and security of Japan, the region and international society.

He said it is believed that North Korea will continue its intention to develop ballistic missiles with a longer range, and could make further provocations.

Matsuno said the government will do everything it can to ensure the peace and security of Japan. He said it will do its best to collect and analyze the necessary information and step up surveillance while maintaining close cooperation with the United States and other parties.