Ukraine launched fresh strikes on Russian energy sites overnight into Sunday, Russian authorities and media reported, while Kyiv denied Russian claims that a Ukrainian drone struck a key Kremlin-occupied nuclear plant.

Drone debris set fire to a fuel storage facility in Russia's southwestern Rostov region, Gov. Yuriy Slyusar reported on Telegram on Sunday. He said residents of nearby homes were evacuated.

The drones also damaged civilian infrastructure in Saratov province, also in southwestern Russia, according to Gov. Roman Busargin. Astra, an independent Russian news channel, said an oil refinery was on fire in the regional capital, Saratov.

Ukraine's General Staff on Sunday confirmed Ukrainian drones had struck the Saratov oil refinery, causing a "large-scale fire." It said the extent of the damage was being clarified, and claimed the refinery has been supplying Moscow's war effort.

The refinery belongs to Russia's state oil enterprise, Rosneft, and produces diesel and gasoline among other types of fuel. Russian authorities did not immediately comment further.

Ukraine has stepped up its attacks on Russia's oil and gas facilities in recent months, arguing the energy sector both funds and directly fuels Moscow's more than 4-year-old invasion.

Meanwhile, Kyiv denied Russia's claims that a Ukrainian drone struck the Russian-occupied Zaporizhzhia nuclear plant, the largest in Ukraine and Europe.

Russian forces captured the plant in the early weeks of the war, and it remains close to the front lines in the southern Zaporizhzhia region, one of four Russia has formally annexed despite lacking full military control or international recognition for its actions.

Russia's state nuclear energy company, Rosatom, said on Saturday that the drone exploded after tearing a hole in the wall of a turbine hall. Rosatom's CEO Alexei Likhachev accused Ukraine of a "deliberate" attack.

"This afternoon, a Ukrainian kamikaze combat drone struck the turbine hall building of Power Unit No. 6, resulting in a detonation," Likhachev said. He added there was no damage to main equipment.

Ukraine's military denied Russia's "yet another propaganda ploy," saying it did not target or strike the plant. The military said in a statement that it adheres to international humanitarian law and is aware of the "consequences of any actions targeting nuclear facilities."

"Along the relevant section of the front line, there was no active fighting at the time of the incident, and no weapons were used," it said.

Rafael Grossi, head of the International Atomic Energy Agency, voiced "serious concern" following the incident in a post on X.

Ukraine's state nuclear supervisory agency said the damage claimed by Russia must be verified by IAEA experts present at the Zaporizhzhia plant as part of a long-term monitoring mission.

The Zaporizhzhia plant has repeatedly come under fire since Russia's full-scale invasion in February 2022, sparking fears of a nuclear accident. Moscow and Kyiv have blamed each other for targeting the plant on purpose.

Elsewhere, Ukraine's air force said Sunday that it had shot down 212 of 299 drones launched by Russia overnight. It said 14 drones had reached their targets, while drone debris fell in five locations.

Russian drones struck the city of Dnipro and an oil refinery in Ukraine's Rivne region, causing fires, authorities said.

Oleksandr Koval, the head of Rivne's regional administration, said no one had been injured at the refinery, and that emergency services were at the site.