North Korea recently deployed about 50,000 special forces along its border with South Korea, Yonhap News reported on Wednesday, citing an unidentified source.

The frontline deployment is the latest of a series of reinforcements by the reclusive regime in recent.

The move comes at a time when Seoul suspects a North Korean submarine is possibly behind the March 26 sinking of a South Korean warship.

Seoul beefed up its monitoring of North Korean forces amid heightened tensions on the Korean Peninsula, though Pyongyang publicly denied its involvement in the naval disaster.