Several US military bases across Europe were put on a heightened state of alert over the weekend, with the level of force protection raised to its second-highest state amid concerns that a terrorist attack could target US military personnel or facilities,

A Pentagon official won't say whether U.S. military bases in the Middle East, Africa or the Indo-Pacific are at increased force protection levels similar to bases in Europe

The security alert for 83,000 U.S. troops in Europe was raised this summer. The war in Ukraine and the Paris Olympics are some of the factors.