The plan will be part of the country's ongoing efforts to bolster its underwater capabilities and combat readiness, Yonhap news agency reports from Seoul.
The Navy has said it plans to add five 1,800-ton submarines to its present fleet of four such craft, and to deploy nine 3,000-ton subs capable of launching ballistic missiles, starting in 2020.
North Korea is believed to have significant superiority in the number of submarines to South Korea, having some 70 vessels, including about 20 1,800-ton Romeo-class submarines.
