Blasts at two air bases in Russia killed three people and injured seven, Russian news services reported Monday, as the Kremlin launched new missile strikes on Ukraine.

Two Tu-95 bombers were damaged and two servicemen wounded when a drone crashed onto the Engels-1 airfield in Russia’s Saratov region, the Russian independent news service Astra reported on its Telegram channel, citing sources it didn’t identify. The region’s governor, Roman Bursagin, also said on Telegram that incidents at military facilities are being investigated, without offering further information.

Three people were killed and five injured when a fuel tanker exploded at an airfield near Ryazan, southeast of Moscow, the state-run Tass news service reported, citing emergency officials.

Reports on the incidents were sent to President Vladimir Putin, Kremlin spokesman Dmitry Peskov told reporters on a conference call, declining to comment further.

Hours after the blasts, Ukrainian officials reported that Russia had launched a new wave of missile attacks and advised citizens to take shelter. Russia’s military has waged a campaign of missile and drone attacks against critical infrastructure in Ukraine aimed at cutting power, heating and water supplies to civilians during winter, prompting an international outcry and accusations that it is committing war crimes.

Russia has blamed Ukraine for a series of blasts at military facilities in Crimea, which Putin annexed in 2014. A flagship bridge linking Russia to Crimea across the Kerch Strait was also damaged in an explosion in October.

Ukrainian officials have mostly avoided claiming responsibility for the attacks, though they subsequently confirmed involvement in a strike that damaged Russian warplanes at a Crimean airfield in August.

The latest incident prompted similar vague comment from Kyiv.

“If something is launched into other countries’ airspace, sooner or later unknown flying objects will return to departure point,” Ukrainian presidential adviser Mikhailo Podolyak said on Twitter.