The Democratic People's Republic of Korea (DRPK) is conducting a live-fire exercise near the disputed north-western maritime border with South Korea.
Held in the Yeonpyeong and Baengnyeong islands, located near the Northern Limit Line (NLL) in the Yellow Sea, the exercise involves all three branches of the North Korean military, the South Korean Joint Chiefs of Staff (JCS) said.
An unnamed South Korean military official was quoted by Reuters as saying that although firing has started, so far no rounds have landed south of the disputed border.
South Korea had enhanced its military readiness by sending warships, early warning surveillance aircraft and fighter jets to the area soon after the notification, in an effort to prepare for a potential clash, the Yonhap News Agency reported.
South Korean Defence Ministry spokesperson Kim Min-seok was quoted by the news agency as saying that the live-fire drill toward southern waters 'implies' North Korea's provocative nature.
"We are carefully monitoring North Korea's exercise to sternly react if any of its shells fall in southern waters," Min-seok said.
Pyongyang had staged a series of similar exercises on 31 March 2013, which resulted in the exchange of hundreds of artillery shell between the two nations.
The drills follow satellite imagery showing heightened activities at North Korea's main nuclear test site in Punggye-ri, raising fears that the communist state might be preparing to conduct its fourth atomic test.
Commenting on atomic test reports, Min-seok said: "As the North could deceit the timing, the South Korean military has maintained a high level of vigilance."