North Korea said on Friday it had fired 18 short-range ballistic missiles during a drill as a demonstration of its willingness to launch a pre-emptive strike against South Korea's "gangsters' regime" if necessary to counter an attack.

North Korean leader Kim Jong Un guided the firing drill of the 600mm "super-large" multiple rocket launchers on Thursday, state news agency KCNA reported.

South Korea said it had detected at least 10 short-range ballistic missiles fired by North Korea off its east coast, calling it a possible display for would-be weapons buyers, including Russia.