Explosion at a US air base in southern Japan injures 4 Japanese soldiers

Prefectural officials said the injuries were not life-threatening, but no other details were immediately known.

An explosion at a storage site for unexploded ordnance at a US military base on Japan's southern island of Okinawa injured four Japanese soldiers, though the injuries are not life-threatening, officials said Monday.

US military personnel gather near the site of an explosion at a storage site for unexploded ordnances in Okinawa. (AP)

The four soldiers sustained finger injuries while working at a facility that belongs to Okinawa prefecture and temporarily stores unexploded ordnance, mostly from wartime and found on the island, local officials said. One of the harshest battles of World War II was fought on Okinawa.

Prefectural officials said the injuries were not life-threatening, but no other details were immediately known.

The U.S. Air Force said in a statement that the explosion occurred at the facility managed by the Okinawa prefectural government at Kadena Air Base's munitions storage area. It said no U.S. servicemembers were involved in the incident.

The Self-Defence Force's joint staff said one of the devices exploded when the soldiers were inspecting it at the facility. The blast occurred when the soldiers were trying to remove rust, NHK television reported.

The SDF said they are trying to confirm what caused the accident.

Monday's accident was believed to be the first ever since the 1974 launch of the Japanese army's unexploded ordnance disposal unit.

Hundreds of tons of unexploded wartime bombs, many of them dropped by the U.S. military, remain buried around Japan and are sometimes dug up at construction sites and elsewhere. Many of them are still found on Okinawa, where about 1,856 tons of unexploded U.S. bombs are believed to remain.

In October, an unexploded wartime U.S. bomb exploded at a commercial airport in southern Japan, causing a large crater and suspending dozens of flights.