Ukraine launched a wave of drone attacks on Russia including the Moscow region on Tuesday hitting at least one oil refinery.
At least 25 drones and seven missiles were used in the large-scale air strikes, Russia's defence ministry said.
One local official said the assault had left at least one refinery in the world's second biggest oil exporter on fire.
Both sides have used drones to strike critical infrastructure, military installations and troop concentrations in their more than two-year war, with Kyiv hitting Russian refineries and energy facilities in recent months.
Russia's defence ministry said it had downed 25 Ukrainian drones over Russian regions including Moscow, Leningrad, Belgorod, Kursk, Bryansk, Tula and Oryol.
Russian local officials reported attacks on a string of energy facilities.
"An attempt by the Kyiv regime to carry out a terrorist attack using 25 drones on objects in the territory of the Russian Federation was stopped," the defence ministry said in a statement.
There was no immediate comment from Ukraine.
Gleb Nikitin, governor of the Nizhny Novgorod region, reported a drone attack on a fuel refinery in the Kstovo industrial zone.
"The Kstovo industrial zone, a fuel and energy complex facility, was attacked by unmanned aerial vehicles," Nikitin said on Telegram. A refinery was on fire, he said. He did not name it.
State news agency RIA cited Russian Railways and reported that a special train that puts out fires was battling a blaze on the territory of Lukoil's refinery in Kstovo.
Lukoil did not immediately respond to a request for comment.
The Kremlin on Monday said a call by Pope Francis for Kyiv to have the “courage of the white flag” and enter negotiations to end Putin’s war was "quite understandable", but NATO's boss Jens Stoltenberg said now was not the time to talk about "surrender".
Ukraine's Foreign Ministry summoned the Vatican ambassador, known as the papal nuncio, to express its "disappointment" with Francis' comments in an interview recorded last month.
In an attempt to defuse the situation and clarify Francis' remarks, his second in command at the Vatican said in a newspaper interview on Tuesday that the first condition for any negotiations is that Russia should halt its aggression.
As the West grapples with how to support Ukraine and the prospect of a sharp change in US policy if Donald Trump wins November's presidential election, Putin has essentially offered to freeze the battlefield along its current front lines, a premise Ukraine rejects.
Moscow's offers to negotiate have invariably been predicated on Kyiv giving up the territory that Moscow has seized and declared part of Russia - more than a sixth of Ukraine.
