Russia's aviation authority announced on Thursday the temporary closure of five airports, including all four Moscow airports and one in Kaluga, located 160km southwest of the capital.
The aviation watchdog Rosaviatsia did not provide a reason for the closures.
In a statement, Rosaviatsia said: "Aircraft crews, air traffic controllers and airport services are taking all necessary measures to ensure flight safety."
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Moscow's Vnukovo International AirportGETTY
General view of Moscow's Vnukovo International Airport
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