Belgium’s defense minister expressed concern on Monday about a series of unidentified drone flights over the weekend near a military base where U.S. nuclear weapons are stored, saying that they seem to be part of a spying operation. Defense Minister Theo Francken confirmed that drones had flown into the area near the Kleine Brogel air base in northeast Belgium in two phases on Saturday and Sunday night. The first phase involved “small drones to test the radio frequencies” of Belgian security services, then later came “big drones to destabilize the area and people,” Francken told public broadcaster RTBF.