The blast occurred while SDF personnel were preparing to carry out bomb disposal operations, Japan’s defence ministry confirmed.
Four troops sustained minor injuries, according to local media reports citing the defence ministry. None of the injuries were life-threatening.
Public broadcaster NHK reported that the explosion may have taken place at a temporary storage site for unexploded ordnance. Officials are working to verify the cause.
“We’ve heard there was an explosion at the SDF facility and also heard there were injuries but we don’t have further details,” said Yuta Matsuda, a local official from Yomitan village in Okinawa, speaking to AFP.
There was no evacuation order issued for nearby communities, local authorities said.
The Kadena Air Base is the largest US military installation in the Asia-Pacific region. Okinawa hosts the majority of US military forces in Japan, a long-standing point of tension among residents.
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Separately, Japan’s defence ministry said a Chinese aircraft carrier group, led by the Liaoning, entered Japan’s exclusive economic zone (EEZ) over the weekend for the first time before conducting drills involving fighter jets.
The group included two missile destroyers and a fast combat support ship, and passed roughly 300 km southwest of Minamitori Island, the ministry said.
“We think the Chinese military is trying to improve its operational capability and ability to conduct operations in distant areas,” a ministry spokesperson said.
Chief Cabinet Secretary Yoshimasa Hayashi told reporters on Monday that Tokyo had conveyed an “appropriate message” to Beijing, though he stopped short of confirming a formal protest.