|Fire exchanged: South Korean army tanks (file picture)|
Official in Seoul say South Korea returned fire after North Korean shells landed in its territorial waters.
YTN news television said shells appeared to have landed in the water north of one of the populated South Korean islands off the west coast of the peninsula.
Earlier today, North Korea announced it would hold live-fire drills in seven parts of the border area.
The area has previously been a flashpoint between the two countries.
In 2010, North Korean artillery fire killed four South Koreans on a border island.
Earlier that year, a South Korean warship sank near the disputed border with the loss of 46 lives.