The Democratic People's Republic of Korea (DPRK) said Tuesday that its nuclear test was an act of self-defense against the US's hostility.

It is "natural just measure for self-defense to react to the US ever-increasing nuclear threat with nuclear deterrence," a spokesman for the DPRK's Foreign Ministry said in a statement released by the official news agency KCNA.

The DPRK's patience has "reached its limit as the US intensified such hostile act", the spokesman said, warning to "take the second and third stronger steps in succession" if the US, its "sworn enemy," continues hostility.

"The DPRK's nuclear test is a just step for self-defence not contradictory to any international law," he added.

The spokesman said that Washington should choose whether to respect the DPRK's right to satellite launches or to persistently pursue a wrong hostile policy which led to the explosive situation.

The DPRK said earlier today it had successfully conducted the third nuclear test in a "safe and perfect" way, aiming to defend national security and sovereignty.