A South Korean weapons expert has indicated that the missile North Korea launched over Japan last week was a new type of ballistic missile.

Shin Jong-woo, representative secretary of the Korea Defense and Security Forum, analyzed images of the missile launched on October 4.

Pyongyang said on Monday that a new type of ground-to-ground intermediate-range ballistic missile flew over Japan and hit the targeted water area in the Pacific that is 4,500 kilometers away.

Shin said the missile seems to have only a main engine. He pointed out the absence of the nozzles of four auxiliary engines that were present on a Hwasong-12 intermediate-range ballistic missile that flew over Japan before.

He said the missile's simple structure allows stable and efficient operation of the engine.

Shin also said the warhead looks shorter and rounder than that of the Hwasong-12 missile, noting that North Korea may be using different designs depending on the shapes of nuclear weapons that would be mounted.

He added that Pyongyang may launch ICBM-class missiles over Japan.