The Japanese government has insisted that it is taking necessary steps to counter North Korea's missile threat, but the ballistic missile that flew over northern Japan on Tuesday exposed the limits to which the country can fully prepare for the highly unpredictable launches.

"We've been completely tracking the movement (of the missile) ever since its launch and are thoroughly ready to protect the lives of the people," Prime Minister Shinzo Abe told reporters as he announced that a missile had crossed over Japan before splashing into the Pacific Ocean.

The Self-Defense Forces did not take actions to intercept the missile, with Defense Minister Itsunori Onodera saying the decision not to blow it out of the sky had been taken because radar data ruled out the possibility of the projectile falling on Japan.