The government decided to maintain close watch and readiness to prepare against the possibility of further provocations by North Korea, and make full preparations for a strong response in the event that the North provokes us again, presidential spokesman Min Kyung-wook told reporters following an emergency meeting of the National Security Council.

The meeting came a few hours after the two Korea exchanged artillery fire across the western maritime border Monday morning after the North staged a live-fire drill that sent artillery shells into southern waters, prompting South Korean residents of border islands to evacuate.

 The North fired about 500 rounds of artillery shells into waters north of the Northern Limit Line in the Yellow Sea from 12:15 p.m. to 3:30 p.m., South Korea's Joint Chiefs of Staff said.

After some 100 rounds fell south of the NLL, the South Korean military shot about 300 artillery shells into North Korean waters with K-9 self-propelled howitzers and dispatched F-15K fighter jets near the maritime border, it said. 

By late afternoon, about 4,000 residents of South Korea's five western border islands returned to their homes after the military lifted an evacuation order it issued hours earlier, officials said.

The residents had been evacuated to temporary shelters. No casualties or injuries were reported. (Yonhap)