The South Korean military has boosted its surveillance against North Korean submarines by deploying five additional anti-submarine aircraft.
South Korea had 11 P-3CK maritime surveillance aircraft in use as of late 2010, but the number would be increased to 16 from 2011, which will be operated from bases in Pohang and Jeju Island.
A military source said the ability to detect submarines is limited with the use of destroyer ships and corvettes that use sonar.
"With the additional anti-submarine surveillance aircraft, we are now able to watch the movements of North Korean submarines very closely," it added.
The additional P-3CK aircraft recently underwent refurbishment in October 2010.