KYIV, Ukraine: Ukraine denied Moscow’s claims that a Ukrainian drone struck the Russian-controlled Zaporizhzhia nuclear plant, as Kyiv on Sunday launched fresh strikes overnight on Russian energy sites.

Ukraine’s General Staff said Ukrainian drones struck the Saratov oil refinery in southwestern Russia, 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. Local Russian Gov. Roman Busargin, said Ukrainian drones had damaged civilian infrastructure, but did not immediately give details. Astra, an independent Russian news channel, said an oil refinery was on fire in the city of Saratov.

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.

“Tonight, our soldiers applied Ukraine’s long-range sanctions against an oil refinery in Saratov, Russia — approximately 700 kilometers (435 miles) from the front line. A significant achievement,” Ukrainian President Volodymyr Zelensky wrote on social media later on Sunday.