The Maritime Self-Defense Force disposed of 14 unexploded artillery rounds Friday, Naha city officials said.
The 14 shells were found during an underwater search ahead of reclamation work in Naha harbor and are believed to have been U.S. weapons dating from World War II, the officials said.
The MSDF detonated the ordnance about 8 meters beneath the surface at 11 a.m., sending up a column of water about 5 meters high.
The 14 weapons included one 150mm, five 200mm and eight 4-inch artillery rounds, the officials said.
They said it is estimated it will take 100 years to get rid of all the unexploded ordnance that litters Okinawa. Two bomb-disposal exercises are scheduled for May 26 and June 2 in Naha, they said.
Okinawa Prefecture, the scene of fierce ground fighting in the closing days of World War II, on Wednesday marked the 30th anniversary of its reversion to Japanese control after 27 years of U.S. military rule.