North Korea says it has successfully test-fired a solid-fuel intermediate-range ballistic missile. It is the first time Pyongyang has announced the launch of a solid-fuel missile of this range that can be fired more quickly than those that use liquid propellants.

The country's ruling Workers' Party newspaper, Rodong Sinmun, reported on Monday that the Missile Administration conducted the successful testing on Sunday.

It reported that the missile had a warhead that travels at hypersonic speeds, and officials verified its "gliding and maneuvering characteristics" and the reliability of the newly-developed "high-thrust solid-fuel engine."

A photo released shows a missile ascending with flames flaring out like a skirt and a massive amount of smoke, typical of a solid fuel propellant.

The country has been working to shift from liquid to solid-fuel propellants in ICBM-class launches and short-range ballistic missile development.

Observers say North Korea is trying to increase its ability to carry out surprise attacks through such a shift also in intermediate-range ballistic missiles.

The observers say the development of warheads that can travel about five times the speed of sound is part of North Korea's five-year defense program, which has entered its fourth year, and that shooting them down will be more difficult.