Ukrainian officials reported a huge fire at the Kombinat Kristall oil depot, which provides fuel to the Engels-2 military airfield in the Saratov region, where Russia’s strategic bomber fleet is located, CNN said in a report.

At least two Russian firefighters were killed while responding to the fire, Roman Busargin, governor of Saratov region, said in a post on Telegram Wednesday. Another specialist was hospitalized, Busargin said.

Images geolocated by CNN showed large balls of flames lighting up the night sky and plumes of smoke continuing to billow from the site on Wednesday morning.

“The destruction of the oil depot raises major logistic challenges for the strategic aviation of the Russian occupiers and significantly reduces their ability to strike at peaceful Ukrainian cities and civilian objects,” Ukraine’s military claimed in its statement.

MNA