The deployment began two or three years ago and seven 7,000-strong divisions are now in place, an unidentified senior government official told Yonhap news agency.
"The threat that North Korea may infiltrate special forces for limited warfare has become real," the agency quoted a separate senior defence ministry official as saying.
The defence ministry refused to confirm the Yonhap report, but President Lee Myung-Bak discussed the North's special warfare capabilities at an unprecedented meeting Tuesday with 150 top officers from all armed services.
At the meeting, Mr Lee hinted strongly that the North was involved in the sinking of a South Korean warship with the loss of 46 lives near the disputed sea border on March 26.
Suspicions are growing that the 1,200-tonne ship was hit by a torpedo from the communist state, which has denied involvement.
Mr Lee said the South must be better prepared to tackle "asymmetric" military threats including special warfare units.
A defence ministry report in 2008 said the North - learning lessons from the Iraq war - had strengthened its special warfare capability by augmenting light infantry units and enhancing their street warfare, night-time and mountaineering training.
The North has about 180,000 special forces, it said, adding they would be used for "multifarious types of attacks and mixed warfare" against the South.
Telegraph
