A fire at a fuel tank near an airport in the Russian Black Sea resort of Sochi has been extinguished, the city's mayor said on Wednesday.

"There were no casualties," the mayor, Alexei Kopaigorodskyi, said on the Telegram messaging platform.

"The airport and the entire transport system are operating as normal."

He said the cause of the fire is being investigated. (Reporting by Lidia Kelly in Melbourne; Editing by Christopher Cushing)