A Japanese Maritime Self Defense Force (JMSDF) Soryu-class submarine collided with a commercial vessel off Kochi Prefecture on Monday, local reports say.
The yet-to-be identified submarine hit the cargo ship with its sail as it was about to surface as part a training evolution, the reports said.
According to first information shared by officials, at least three submariners were injured in the incident. The extent of damages sustained by the submarine is yet unknown.
Japan Coast Guard officials said no injuries had been reported on the cargo ship.
Japan has a total of eleven Soryu-class submarines in its fleet, with the delivery of another four pending. The 2,950-ton submarines are propelled by a Diesel-Stirling-electric main engine and feature air-independent propulsion (AIP) systems, which help them stay under water for weeks, without having to surface. They are armed with torpedoes and Harpoon anti-ship missiles.