North Korea's Kim Yo Jong vows immediate response to provocation

North Korea's army will immediately launch a "baptism of fire" in response to any provocation, Kim Yo Jong, the powerful sister of leader Kim Jong Un, said on Sunday, in comments carried by state news agency KCNA.

The remarks come after South Korea's military said the North fired more than 60 artillery rounds on Saturday near their disputed maritime border, following a similar volley of more than 200 there the previous day.

"Let me be clear once again that our army has its trigger already unlocked," Kim Yo Jong said in a statement carried by KCNA.

"Our army will immediate launch a baptism of fire in case of even a small provocation."

Although South Korea held its own fire drills in the sea on Friday in response to the artillery shells, the Yonhap news agency said there was no plan to do so after Saturday's events.

Friday's duelling drills sparked warnings for residents of South Korean border islands to seek cover in bomb shelters, though there was no report of shells crossing the maritime border.

In the statement, Kim denied the Saturday firing and said the North detonated explosives instead as a deception.