International Desk: Ukrainian drones struck two air bases deep inside Russian territory, the Kremlin said Monday, shortly before Russian forces unleashed a massive missile barrage in Ukraine that struck homes and buildings and killed civilians.

The unprecedented attack in Russia threatened a major escalation of the nine-month war because it hit an airfield housing bombers capable of carrying nuclear weapons. President Vladimir Putin has threatened to use all available means to defend his land, a remark many have interpreted to include nuclear weapons, reports The Associated Press.

Russia has been launching almost weekly bombardments of Ukraine in retaliation for another bold attack – the Oct. 8 truck bombing of a vital bridge linking its mainland to the Crimean Peninsula.

On Monday, Putin tried to show his country could bounce back from that embarrassment by driving a car across the partially repaired bridge. Putin personally opened the 19-kilometer (12-mile) bridge in 2018 as part of an expensive effort to solidify his claim on Crimea, which Russia illegally annexed in 2014.