Editor's note: This is a developing story and is being updated.
Explosions rocked an oil refinery in the Russian city of Slavyansk-on-Kuban amid a Ukrainian drone attack overnight on Dec. 17, media reported.
Just before midnight on Dec. 16, a drone attack and explosions took place in Russia's Saratov Oblast, Telegram channel Exilenova+ reported.
Slavyansk-on-Kuban is located in Krasnodar Krai in southern Russia near the Azov and Black seas. Saratov Oblast, at its closest point, is located about 330 kilometers (205 miles) from Ukraine's northeastern border with Russia.
Kyiv has not yet commented on the attack, and the reports could not be independently verified.
Ukraine regularly strikes Russian military and energy infrastructure in an effort to diminish Moscow's fighting power as it continues to wage its war against Ukraine.
Russian energy directly funds the Kremlin's war, and energy infrastructure sites are considered military targets by Kyiv.
Ukrainian forces launched a large-scale attack against Russian military and oil facilities, striking assets in Russia and in occupied territories, including Crimea, Ukraine's General Staff reported on Dec. 14.
The Slavneft-Yanos oil refinery in Yaroslavl, one of Russia's five largest, was struck in a drone attack overnight on Dec. 12, Ukraine's General Staff confirmed later the same day.
Open letter to President Trump: Protect legal Ukrainian workers in US