The South Korean military said an unidentified object that appeared to be a periscope was spotted in the West Sea on Wednesday.

The Joint Chiefs of Staff(JCS) said that police on highway patrol reported to military authorities on Wednesday morning that the object, presumed to be a submarine periscope, was moving northward off the western island of Haengdam, South Chungcheong Province. 

A JCS official said that it is unlikely a foreign submarine infiltrated shallow waters so close to South Korea's shoreline, but the military has blocked off and is patrolling the area.