North and South Korea have exchanged fire across the disputed western maritime border. There has been no indication that the shelling by either side was aimed at any particular target.
North Korea announced earlier on Monday that it would hold live fire drills in seven parts of the border area. South Korea says it returned fire after North Korean shells landed in its territorial waters.
South Korean officials said residents on the south's Baengyeong island, close to the maritime boundary, had taken shelter as a precaution.
The area has been a flashpoint between the two nations, the ABC reports. In late 2010, four South Koreans were killed on a border island by North Korean artillery fire.