July 6 (Reuters) - The Ukrainian military said on Monday that Ukrainian drones had bombed Russia's largest oil refinery in the Siberian city of Omsk, in what could be one of Kyiv's farthest attacks during the war.

Russian authorities confirmed the attack.

The Ukrainian General Staff said in a statement that the attack caused a fire at the Omsk refinery, located about 2,700 kilometers from Ukrainian-controlled territory and near Russia's border with Kazakhstan.

Vitaliy Khutsenko, the governor of the Omsk region, said that Ukraine attacked the refinery, adding that Russian air defenses destroyed most of the drones involved in the attack.

Khotsenko stated in a post on the Russian messaging app (Max) that there were no casualties and that emergency services were working on the site.

The extent of the damage to the refinery is not yet clear.

Ukrainian President Volodymyr Zelensky described the attack as "an important achievement for the Ukrainian armed forces... Siberia is now also within range of Ukrainian precision strikes."

Ukrainian defense technology company Firepoint said its upgraded FB-1 drones carried out the attack, describing it as a record for attack drones "not only in Ukraine but worldwide. Before this, the Omsk oil refinery was beyond the reach of Ukrainian drones."

Sources told Reuters that the Gazprom Neft-owned Omsk refinery processed about 23 million tons last year, or about 460,000 barrels per day.

Ukraine is escalating its attacks on Russian oil refineries, sometimes causing severe fuel shortages.