Ukraine has dramatically increased the number of attacks launched against Russian oil refineries in recent months, sparking fuel shortages and price rises in some parts of the country, BBC Verify and BBC Russian have found.
Drone strikes on refineries - some deep inside Russia - soared in August and remained high in September, an analysis of Russian media reports and verified footage showed.
Some 21 of the country's 38 large refineries - where crude oil is converted into usable fuel like petrol and diesel - have been hit since January, with successful attacks already 48% higher than the whole of 2024.
Ordinary Russians appear to be feeling the impact of the strikes, with verified videos showing long queues at petrol stations. Some garages have suspended operations to wait out the crisis rather than work at a loss, one manager told Russian media.
Ukraine's security service, the SBU, did not respond to a request for comment. But President Volodymyr Zelensky has said damaging Russia's oil industry is a key means of forcing Russia to the negotiating table.
The most effective sanctions – the ones that work the fastest – are the fires at Russia's oil refineries, its terminals, oil depots, the Ukrainian leader said in a September address. We have significantly restricted Russia's oil industry, and this significantly restricts the war.
Our analysis shows reported attacks reached a record level in August, with 14 refineries targeted by Ukrainian drones, and eight in September. The increase came after a brief lull coinciding with a flurry of diplomacy, during which President Donald Trump attempted to broker a ceasefire deal between Kyiv and Moscow.
Some of the strikes have been launched against facilities deep inside Russia. In late September, the SBU successfully hit the Gazprom Neftekhim Salavat oil refinery in the Bashkortostan region twice.
Satellite images showed smoke billowing from the facility - which is more than 1,100km (683 miles) from the Ukrainian border - after the attack.
Kyiv has also attacked some of Russia's most lucrative facilities. A refinery near Volgograd has been targeted six times this year - with an attack in August forcing it to halt operations for a month. The large Ryazan plant near Moscow - capable of producing 340,000 barrels per day - has been hit five times since January.
Ukrainian strikes appear to be pursuing two targets - large refineries essential to civilian supplies and those closer to the border used to supply troops fighting in Ukraine, Vladimir Milov, a former deputy energy minister under Vladimir Putin and now an exiled opposition politician, told BBC Verify.
Justin Crump, an ex-British army officer and CEO of the risk consultancy Sibylline, told BBC Verify that Ukraine had long targeted Russia's oil and gas industry. But he noted that the flurry of strikes showed that the military and security services have now settled on the tactic as a core campaign.
It is difficult to measure the extent to which the strikes are impacting the output of petrol and diesel as Russia classified statistics relating to gasoline production in May 2024 amid an earlier spate of attacks on refineries.
But BBC Verify's analysis found that at least 10 oil refineries have been forced to fully or partially suspend operations since August, and the Reuters news agency has reported that on certain days national production has declined by as much as a fifth.
There is some evidence that the refinery strikes are having an impact on civilian life in parts of Russia. Videos confirmed by BBC Verify have shown long queues at petrol stations in the far east and on a highway between St Petersburg and Moscow, while Kremlin-installed officials have introduced rationing of gasoline in occupied Crimea.
While Russia has traditionally seen price increases spurred on by summer travelling and oil refinery maintenance, the drone strikes are exacerbating it.
Retail petrol prices have surged, while wholesale prices - the cost at which retailers buy from producers - have risen even faster, growing by 40% since January.
The tightly controlled domestic media has hinted that drone strikes are a key factor for the shortages, with the daily business newspaper Kommersant attributing the shortfall to unscheduled refinery shutdowns.
But civilians in western Russia - including the Moscow and Krasnodar regions - appear to be largely unaffected. Some of those who spoke to the BBC said they were unaware of the shortages elsewhere in the country.
Russian officials have insisted that the situation remains under control. During a press briefing this week Kremlin spokesperson Dmitry Peskov said the government is taking the necessary measures to address shortages.
The extent to which the strikes are impacting Moscow's ability to use oil revenues to fund its war in Ukraine is also unclear.
Despite the significant impact, the ongoing campaign shows relentless pressure on Russia's oil supplies and might continue to slow its military operations.