South Korean officials say the DPRK has completed nuclear test technical preparations and underground detonation could occur any time.

Yonhap News Agency also quotes South Korean experts as saying the DPRK aims to build a new 3,000-ton submarine armed with 3 Satellite-Launched Ballistic Missiles, or SLBMs.

This comes after the DPRK on Sunday carried out a submarine-launched ballistic missile. The DPRK's official news agency KCNA says the test-fire aimed to confirm the stability of the underwater ballistic launching system, in the maximum depth of waters.