Russia has blamed Israel for the loss of an aircraft to Syrian fire with the loss of 15 servicemen on board and threatened a response.
Israeli pilots carrying out attacks on Syrian targets "used the Russian plane as a cover, exposing it to fire from Syrian air defences," a statement by the Russian military said.
"15 Russian servicemen died," it said, adding that Russian reserved "the right to proper retaliatory actions" against Israel.
Earlier, Russia's defence ministry said one if its military aircraft with 15 people on board disappeared from radar screens over Syria at the same time that Israeli and French forces were mounting air attacks on targets in Syria.
A US official said Washington believed the reconnaissance aircraft was inadvertently shot down by Syrian anti-aircraft fire.
Around the time the plane disappeared, the Syrian coastal city of Latakia, near a Russian airbase to which the aircraft was returning, came under attack from "enemy missiles" and missile defence batteries responded, Syrian state media reported.
The defence ministry in Moscow said the aircraft was returning to the Russian-run Hmeymim airbase in Latakia province when it disappeared from radar screens.
The plane was over the Mediterranean Sea about 35 km from the Syrian coastline, Russia's TASS news agency quoted the ministry as saying in a statement.
"The trace of the Il-20 on flight control radars disappeared during an attack by four Israeli F-16 jets on Syrian facilities in Latakia province," the statement was quoted as saying.
"At the same time Russian air control radar systems detected rocket launches from the French frigate Auvergne which was located in that region."