All four of Moscow's airports including another about 100 miles southwest of the Russian capital were temporarily shut down for undisclosed security concerns, authorities said.

Russia's aviation authority announced the temporary closure of all Moscow airports and the Kaluga airport. The statement did not specify reasons but emphasized that crews and controllers are ensuring flight safety.

All four of Moscow’s airports have been temporarily closed without any reason given, according to Russia ’s aviation watchdog. ‘Aircraft crews, air traffic controllers and airport services are taking all necessary measures to ensure flight safety,’ the statement from Rosaviatsia said.

"To ensure the safety of civil aircraft flights, temporary restrictions have been introduced on the operation of Sheremetyevo, Domodedovo, Vnukovo, Zhukovsky and Kaluga airports," Rosaviatsiya said on Dec.

The authorities temporarily closed Moscow's four airports, citing safety reasons, but the restrictions were later lifted.

Russian authorities on Thursday closed all four of Moscow’s airports, plus a fifth one in a city about 100 miles southwest of the country’s capital, citing unspecified safety concerns.