"That range would not be enough to reach the lower 48 states or the large islands of Hawaii, but would allow it to reach all of Alaska," he wrote in a blog post.

With a summit of leaders from the Group of 20 nations to be held in Germany later this week, Japan's Prime Minister Shinzo Abe said he would ask the presidents of China and Russia to play more constructive roles in efforts to stop the North's arms programme.

"Leaders of the world will gather at the G20 meeting. I would like to strongly call for solidarity of the international community on the North Korean issue," Mr Abe said.

It was the fourth ballistic missile launched by the North since South Korea's President Moon took office in May, vowing to use dialogue as well as pressure to bring Pyongyang's nuclear and missile programmes under control.