The North Korean Navy has deployed a new submarine to strengthen the intensity of maritime infiltration drills being conducted near its bases off the East Sea and Yellow Sea, a government source has said.

“Our military is closely monitoring activities of the North Korean military because it is unusual for the North to strengthen the intensity of its submarine drills,” South Korean Defence Minister Kim Kwan-jin said.

The new 35m-long Sango Class Shark submarine will participate along with five to six unidentified submarines in naval manoeuvres.

The nation recently deployed a new 40m-long Sango submarine into service.