Attacks on airfields inside Russia would deal a powerful psychological blow, senior Western officials said on Tuesday, saying it meant Moscow would have to think much more carefully about how to keep its long-range bombers safe.

Engels Air Base, located near the city of Saratov and at least 600 km from the nearest territory of Ukraine, and two other airfields have been attacked by drones in the past two days. Ukraine did not take responsibility for the attacks, but celebrated them, and Russia responded with a “massive attack on Ukraine’s military command system.”

Senior Western officials, who spoke on condition of anonymity, said the strikes were the deepest inside Russia since its February 24 invasion of Ukraine.

“If it were them (Ukrainians) … they are demonstrating that they can operate as they please in Russia, and that will deeply worry the Russians,” one official said. “Psychologically, I think it takes a toll.”

Officials said Russia had kept its long-range strategic bombers at Engels, but would now have to consider moving them.

“This could lead to the deployment of these bombers in scattered locations,” the official said. “It certainly makes the Russians less confident … (that) wherever they are safe,” they added.