OMSK, Russia, July 7 (Reuters) - Motorists are queuing for fuel in the Russian city of Omsk after Ukrainian drones hit the country's biggest oil refinery in one of their deepest attacks inside Russia since the start of the war.

Reuters video showed a long but orderly line of vehicles waiting at a filling station on Monday night, a few hours after the attack. A Reuters witness in the Siberian city said there were more queues on Tuesday but waiting times were moderate — around 20 minutes — and fuel was still available.

On the social media network VKontakte, some people complained of needless panic-buying by drivers they called "morons".

Regional governor Vitaly Khotsenko said local authorities had discussed the fuel situation and all necessary measures were being taken to "normalise" logistics and deliveries to private filling stations.

Local media outlet NGS55.RU said one large private network had completely halted petrol sales to individual motorists.

Ukraine has intensified attacks on Russian energy infrastructure in the past months with the primary aim of crippling the source of funding for Moscow's war effort, leading to widespread fuel shortages felt by the Russian population.

Sources told Reuters that the Gazprom Neft-owned SIBN.MM Omsk refinery that was hit processed around 23 million metric tons last year, or around 460,000 barrels per day.

It is Russia's largest producer of gasoline, and any disruption to its operations would likely exacerbate fuel shortages.

Russia, for its part, has targeted Ukraine's energy sector and power grid throughout more than four years of war. Within the past week, it has carried out two heavy attacks on Kyiv that have killed dozens of people.

"Facilities at the Omsk oil refinery were damaged as a result of (Monday's) attack. No plant personnel were injured. Damage assessment is currently under way, and competent services have organized restoration work," Anatoly Seryshev, President Vladimir Putin's representative in Siberia, said in a statement.

Putin's point man on energy, Alexander Novak, described the overall fuel market situation in the country as tight, given the summer peak in demand and what he called, "Unscheduled refinery maintenance."