South Korean experts say the projectiles North Korea launched on Thursday may be a modified version of the Russian short-range ballistic missile, Iskander.

North Korea said on Friday that it conducted test-firings of long-range cruise missiles on Tuesday and "tactical guided missiles" on Thursday.

South Korean experts say the tactical guided missiles are likely to be a modified version of the Iskander that descend on an irregular trajectory.

South Korea's military says the missiles reached an altitude of roughly 20 kilometers.

The experts say that at such a relatively low height, the missile could be harder to detect or to intercept.

As for the cruise missiles fired on Tuesday, there are views that they could be a new type first displayed at a defense exhibition held in Pyongyang last October.

North Korea's announcement of the missile launches referred to what it called a "missile warhead institute" for the first time. The institute was described as an entity under the Academy of Defense Science.

Experts say the reference is likely to be a sign that Pyongyang will start strengthening the development of warheads. North Korea's five-year defense plan calls for the development of a missile with multiple warheads.

North Korean media also said on Friday that leader Kim Jong Un has visited a "munitions factory producing a major weapon system."

The faces of some officials shown in photos with Kim were blurred. South Korean media say analysts view this as a sign that the facility is very important, or that the North wants to avoid the officials from becoming the targets of foreign sanctions.