North Korea will immediately launch a military strike in response to any provocation, Kim Yo Jong, the powerful sister of leader Kim Jong Un, said on Sunday.
The remarks come after South Korea's military said the North had fired more than 60 artillery rounds on Saturday near their disputed maritime border, following a similar volley of more than 200 the previous day.
North Korea was firing shots again on Sunday, South Korea's Yonhap news agency reported, citing the South's military.