“The drones were neutralised, but a fire broke out as a result of the fall of one of the devices,” the operational headquarters of the region in southern Russia said on the Telegram messaging app.

The fire was extinguished and there were no casualties as a result of the fire itself, the administration said. Preliminary information indicated, however, one person had died of a heart attack, it added.

Roman Siniagovskyi, head of the Slavyansk administrative district, said on Telegram that refinery workers were evacuated and there was no threat to nearby populated areas from the incident.

Separately, Moscow’s mayor Sergei Sobyanin said two drones were destroyed near the Russian capital, with no damage or injuries reported.

Russia has accused Ukraine of using drone and missile strikes to disrupt its three-day presidential election that is set to hand President Vladimir Putin his fifth term in office. The election concludes on Sunday.

Ukraine’s president Volodymyr Zelensky did not directly mention the reported intensified attacks by Kyiv forces in his nightly video address on Saturday, but he thanked his military forces and intelligence for new “long-range capabilities.”