The Democratic People's Republic of Korea says it will keep building a nuclear arsenal, regardless of new UN Security Council sanctions, saying they are "unfair, illicit and immoral".

The DPRK's KCNA news agency said the military had been ordered to place nuclear warheads "on standby", for pre-emptive use at any time. It said Kim Jong Un gave the order as he supervised military exercises involving newly-developed rocket launchers. The agency did not mention the date of the exercises, but said South Korea was within range of the new weapons.