FILE PHOTO: A view shows oil pump jacks outside Almetyevsk, in the Republic of Tatarstan, Russia July 14, 2025. REUTERS/Stringer/File Photo

LONDON (Reuters) - Russia's oil pipeline monopoly Transneft has warned producers they may have to cut output following Ukraine's drone attacks on critical export ports and refineries, three industry sources said on Tuesday.

In a statement on its website, Transneft described the news as "fake" and part of the West's "information war" against Russia.

Kyiv has stepped up attacks on Russian energy assets since August in a bid to impede Moscow's war effort in Ukraine and reduce the Kremlin's revenues as attempts to secure an end to the conflict through peace talks have stalled.

OIL AND GAS - RUSSIA'S KEY SOURCE OF FINANCING

Oil and gas revenues have accounted for between a third and half of Russia's total federal budget proceeds over the past decade, making the sector the single most important source of financing for the government.

Ukrainian drones have hit at least 10 refineries - cutting Russia's refining capacity by almost a fifth at one point - and damaged its leading Baltic Sea ports of Ust-Luga and Primorsk, Ukrainian military officials and Russian industry sources said.

Russian authorities have not publicly commented on the extent of the damage or its impact on production and exports.

However, Transneft, which handles more than 80% of all the oil extracted in Russia, has in recent days restricted oil firms' ability to store oil in its pipeline system, two industry sources close to Russian oil firms told Reuters.

Transneft has also warned producers it may have to accept less oil if its infrastructure sustains further damage, the two sources said.

The attacks could force Russia, which accounts for 9% of global oil production, to ultimately cut output, said the two sources and a third source familiar with oil pumping operations.

The three sources asked not to be named due to sensitivity of the issue.

"The appearance of such fake news with reference to some unnamed sources in the Russian fuel and energy complex causes damage to the image of PAO Transneft," Transneft said in its statement.

"It can only be caused by the attempts to destabilize the situation within the framework of the information war unleashed by the West against the Russian Federation," it added.

DRONE STRIKES: 'THE FASTEST WORKING SANCTIONS'?

The West has imposed successive waves of sanctions on Russia over its invasion of Ukraine, focusing heavily on its oil and gas sector. But Moscow has managed to re-route most oil exports to Asia, where India and China are its primary buyers.

Last week, Ukrainian drones hit Russia's biggest oil port of Primorsk for the first time since the war began in 2022, temporarily forcing operations there to shut down.

Primorsk has capacity to export more than 1 million barrels of oil per day, or more than 10% of Russia's total oil production.

Ukrainian President Volodymyr Zelenskiy said the strikes had inflicted significant damage and called attacks on Russian oil infrastructure "the sanctions that work the fastest".

Reuters could not verify the extent of the damage from the strikes.

Russia, unlike leading OPEC producer Saudi Arabia, does not have significant capacity to stockpile oil.

Primorsk partially resumed operations on Saturday, though it remained unclear how long it may take to complete full repairs, the two sources said.

Russian had already lost some oil exporting capacity following another drone attack targeting the Ust-Luga oil terminal on the Baltic Sea in August, according to industry sources.

The Organization of the Petroleum Exporting Countries and its allies including Russia - a group known as OPEC+ - have been increasing production since April after years of cuts aimed at supporting the oil market.

Under the latest OPEC+ agreement, Russia's oil production quota is due to rise to 9.449 million barrels per day this month from 9.344 million bpd in August.

"Russia's ability to ramp up oil production is now under threat due to limited storage capacity," U.S. bank J.P. Morgan said in a note.

Refinery outages, meanwhile, will also weigh on production due to crude storage congestion from lower refinery runs, Goldman Sachs wrote.

Both banks said production will decline only modestly as Asian buyers still had appetite for Russian crude.

(Reporting by Reuters. Editing by Joe Bavier and Mark Potter)