MOSCOW (Reuters) - Russian and U.S. air forces held a joint training exercise in Syria on Tuesday meant to prevent dangerous encounters between their aircraft, Russia's defense ministry said.

Syria's skies have become increasingly crowded since Russia on Sept. 30 joined the Syrian air force in bombing insurgent targets, while a U.S.-led coalition pursues a separate air strike campaign in the country's civil war.

"There was a joint exercise with air crews and ground troops from the Russian and U.S. air forces," General Andrei Kartapolov said in a statement.

He said the exercise entailed Russian and coalition jets practicing close encounters in a special zone at a minimum distance of three aeronautical miles. Crews practiced communicating in English and Russian, he added.

Kartapolov also said Russia and Israel, Syria's neighbor to the southwest, were informing each other continually on the situation in Syrian air space.

(Reporting by Polina Devitt; Editing by Jack Stubbs and Mark Heinrich)