South Korean President Park Geun-Hye on Friday promised a harsh response to any military provocation by North Korea, after its leader Kim Jong-Un ordered the country's nuclear arsenal on standby.

"If North Korea launches a provocation, we must respond with stern punishment to clearly show the price North Korea has to pay and our determination to protect our nation," Park said in a televised speech at a ceremony for newly commissioned military officers.

Following the adoption late Wednesday of unprecedentedly harsh sanctions against Pyongyang by the UN Security Council, Park warned of a "fiercer" North Korean backlash than normal.

Hours after the sanctions resolution was unanimously passed, the North fired six short-range rockets into the sea off its eastern coast -- an almost routine response to condemnation by the international community.

The rocket launches were personally monitored by Kim Jong-Un who, according to state media, also ordered North Korea's nuclear warheads to be deployed "on standby so as to be fired at any moment".

Park said the South would stick to its strategy of squeezing Pyongyang into submission over the issue of denuclearisation.

READ: North Korean leader Kim Jong-Un orders nuclear arsenal on 'standby'