A Navy sailor died after falling overboard while attending a maritime drill in the East Sea on Wednesday, the Navy said.

The Navy sergeant aboard a fast patrol boat fell into the water during a live-fire exercise in the East Sea in the afternoon, the Navy's 1st Fleet said.

He received first aid treatment and was sent to a nearby hospital but was pronounced dead, the armed service said.

The Navy said it is looking into the cause of the accident.

He is known to have fallen into the water as his ankle was entangled in a rope in the process of towing a shooting target, according to sources.

The live-fire drills involving two fast patrol boats were held separately from the Navy's large-scale maritime drills held ahead of West Sea Defense Day on Friday, which commemorates fallen soldiers who died in action while defending the Northern Limit Line from 2002-2010, according to the Navy. (Yonhap)