SEOUL, Korea, Republic Of -- An accidental explosion at a South Korean naval base on Tuesday left three soldiers dead and another injured, South Korea's Defence Ministry said.

Military authorities are investigating the blast that occurred during repair work of a submarine at the base in the southeastern port town of Jinhae, but the possibility of an attack was considered very low.

The explosion occurred when the soldiers opened the hatch of the docked submarine and was strong enough to blow one of the dead soldiers into the sea, said a ministry official, who didn't want to be named, citing official rules.