North Korea will continue to develop "formidable striking capabilities" that cannot be bartered or sold for anything, leader Kim Jong Un said, according to state media on Monday, as he visited workers involved with the country's biggest missile test.

Kim was meeting with officials, scientists, technicians and workers who contributed to a missile launch on Thursday, which North Korea said was its largest intercontinental ballistic missile (ICBM), state news agency KCNA reported.