The defence ministry said recent strikes on refineries in cities including Moscow, Yaroslavl, Ust-Luga, Perm, Saratov and Syzran had put 51 per cent of Russia's oil refining capacity out of action.
The claim could not be independently verified.
Both Moscow and Kyiv have intensified their aerial assaults as progress along the 1200km front line has largely ground to a halt.
Ukrainian forces have repeatedly attacked refineries from Moscow to Siberia, sparking a widespread fuel crisis in Russia earlier in 2026 that forced authorities to restrict petrol sales.
Russian officials have not publicly revealed any data on damage caused to the country's oil infrastructure.
However, President Vladimir Putin said in a rare admission on October 1 that the strikes had cost Russia roughly one per cent of its gross domestic product.
"They started attacking oil refineries and openly declared the goal of damaging our economy. Did they achieve their goal? Partially," Putin said at a meeting of the Valdai Club forum of international foreign policy experts.
Ukrainian Defence Minister Yevhenii Khmara said analysts from Ukraine's intelligence services, the General Staff, and the defence ministry had assessed the strikes' effects.
"Fifty-one per cent of struck refining capacity is a significant blow to the enemy's economy, to its ability to carry out aggression and supply its troop groupings. Our deep strikes continue to bring the war to Russian territory," he said.
Russia has historically been the world's third-largest producer of refined fuel products from crude after the US and China.
Some of Russia's 32 refineries have been hit as many as 15 times since the start of the war, and one refinery has been hit every three days in recent months, creating a cycle of damage and emergency repairs that could degrade units long term, according to the International Energy Agency.
Ukrainian strikes have also increasingly targeted the more complex equipment that removes impurities from fuel, which takes months to repair.
The International Energy Agency says diesel output has fallen by about 30 per cent, and drivers have had to wait up to 40 hours to fill up at petrol stations.
Russian refiners have tried to compensate by delaying scheduled maintenance and bringing mothballed units back online.
Another response has been to lower fuel quality standards to maintain petrol supplies, which risks damage to engines and pollution control equipment.
The Kremlin has also banned diesel exports, pushing global prices higher and prompting US President Donald Trump on September 13 to urge Ukraine to stop hitting refineries.
A Russian drone attack killed one person and injured six more in the Ukrainian city of Kharkiv, mayor Ihor Terekhov said late on Sunday.
Vehicles and an administrative building were set alight and apartment buildings were damaged, he said.
Russia's defence ministry said on Monday that it had struck an electrical substation in the Kharkiv region, as well as energy and port infrastructure and maritime vessels used by Ukraine's military.
Ukraine's air force said Russia launched 205 drones overnight into Monday, of which 172 were shot down or suppressed.
Ukraine has struggled in recent weeks to fend off Russia's intensified aerial attacks on cities that include ballistic missiles and high-flying jet-powered drones.
Presidential adviser Serhii "Flash" Beskrestnov said on social media that 12 automated turrets had been installed in Kyiv to counter jet-powered Shahed drones, with more planned.
He described the turrets as artificial intelligence-controlled machine guns.
The Russian defence ministry said its forces downed 199 Ukrainian drones over Russian regions overnight, as well as the illegally annexed Ukrainian peninsula of Crimea and the Black Sea.
