A new drone attack blamed on Ukraine caused a fire at a refinery in southern Russia, the Krasnodar regional authorities said on Sunday morning, adding that one person had died after suffering a suspected heart attack.
"The fire on the territory of the Slavyansk oil refinery has now been completely extinguished. According to preliminary information, one person died at the time of the drone attack, the preliminary cause of death being a heart attack," the Krasnodar region operational headquarters said on Telegram.
"There are no casualties as a direct result of the fire, there is also no threat to the settlement," it said.
Roman Sinyagovsky, head of the Slavyansk Municipal District, said on Telegram one plant worker was injured and blamed the attack on Ukraine.
The Slavyansk-on-Kuban refinery is located in the Krasnodar region, east of the Sea of Azov.
Drone attacks on refineries and energy sites in Russia have increased this week in the run-up to a presidential election guaranteed to cement President Vladimir Putin's hardline rule.
A fire broke out at a refinery in Samara, around 1,000 kilometres (620 miles) from the Ukrainian border, following drone attacks on Saturday.
An oil refinery was also targeted by a drone strike in Ryazan on Wednesday, causing casualties, while another refinery was targeted outside the city of Nizhny Novgorod on Tuesday.
Two people died following drone strikes in the Russian city of Belgorod on Saturday.
Putin has vowed that Ukrainian attacks on Russian territory will not go "unpunished".