At least 10 U.S. troops were injured Friday, two seriously, in an Iranian attack on Prince Sultan Air Base in Saudi Arabia, according to U.S. officials familiar with the matter.

The strike on the heavily defended base also damaged at least two U.S. Air Force refueling aircraft, the officials said. They spoke on the condition of anonymity because they were not authorized to discuss the incident with the news media. It was not immediately clear how badly the planes were damaged.