April 22 (Reuters) - A large contingent of Russian firefighters was battling a blaze for the third day on ‌Wednesday at the Tuapse oil refinery on the Black ‌Sea after a Ukrainian drone attack, and officials said air quality in ​the city had sharply deteriorated.

On Tuesday, two industry sources said the Tuapse oil refinery, which sells most of its products for export, had halted operations following the April 16 attack.

On Wednesday, the ‌general headquarters of Russia's ⁠southern Krasnodar region said: "In Tuapse, firefighting operations are going on for the third day at a ⁠large fire at the sea terminal after a drone attack by the Kyiv regime."

The headquarters said 276 firefighters and 77 vehicles ​had been ​drafted into the operation.

It said ​byproducts from the fire, mixed ‌with rainfall, had created a "black coating" in areas around the terminal.

Atmospheric readings, it said, showed concentrations two to three times permitted concentration levels of benzene, xylene and soot and residents were urged to remain indoors, keep windows shut and wipe down ‌surfaces.

"The situation will normalise as soon ​as the fire is extinguished," it ​said.

Ukraine has increased attacks ​on Russia's energy infrastructure as the U.S., which ‌had brokered peace talks to ​stop the conflict ​with Russia, has shifted its focus to the war in Iran.

According to Russian officials, attacks on April 16 and ​April 20 on ‌the city of Tuapse damaged transport infrastructure at the ​port and set oil product storage on fire.

(Reporting by ​Reuters; Editing by Kim Coghill)