The U.S. Air Force is upgrading two of its European bases to better secure nuclear weapons stored there, according to a watchdog group.
Commercial satellite imagery shows the work underway at the Incirlik Air Base in Turkey and Aviano Air Base in Italy, according to a report Thursday from the Federation of American Scientists, a nonprofit based in Washington, D.C., which opposes the proliferation of nuclear weapons.
The Defense Department last week announced it was offering voluntary evacuations to almost 1,000 mostly Air Force family members from Incirlik "out of an abundance of caution" as unrest spreads in the region. The U.S. recently began using the airbase -- located less than 100 miles from the Syrian border -- to launch airstrikes against Islamic State militants in Syria.
The construction work -- which includes new security fencing, lighting and sensors -- raises doubts about the security of the nuclear weapons stored in the region, according to Hans Kristensen, director of the Nuclear Information Project at FAS.
"The upgrades indirectly acknowledge that security at U.S. nuclear weapons storage sites in Europe has been inadequate for more than two decades," he wrote. "And the decision to upgrade nuclear security perimeters at the two U.S. bases strongly implies that security at the other four European host bases must now be characterized as inadequate."
Incirlik Air Base is the largest nuclear weapons storage site in Europe with 25 underground vaults, each of which can hold up to four bombs for a maximum total base capacity of 100 bombs, according to FAS. There are an estimated 50 B61 thermonuclear bombs stored there -- a quarter of the U.S. stockpile of the weapon, which can be carried by F-16s and other aircraft.
