North Korea has fired an intermediate-range ballistic missile that flew over Japan before landing in the northern Pacific Ocean.

It was the second aggressive test-flight over the territory of the close US ally in less than a month and it followed the sixth and most powerful nuclear test by North Korea to date on September 3.

South Korea's Joint Chiefs of Staff said the missile travelled about 3,700 kilometers (2,300 miles) while reaching a maximum height of 770 kilometers (478 miles).