The Russian state news agency TASS reported that a Russian IL-20 military aircraft with 14 personnel on board disappeared over the Mediterranean on Monday.
The defence ministry in Moscow said the aircraft was returning to the Russian-run Hmeymim airbase when, at about 11:00 p.m. Moscow time (20:00 GMT) on Monday, it lost radar contact.
The Ministry of Defence said 15 Russian military service people had died because of what it described as Israel's irresponsible actions.
A search for the plane is underway.
The news site said the plane is capable of monitoring Syrian skies in real time.
The Russian defence ministry also said that rockets had been launched from the French Navy's frigate, The Auvergne, which was in the area at the time.
U.S. officials told CNN and Reuters that Washington believed Syrian air defenses had accidentally shot down the Russian aircraft.
"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.
A military official quoted then on state media said Syrian air defences intercepted some missiles coming from the sea.
During the more than seven-year conflict in neighbouring Syria, Israel has grown deeply alarmed by the expanding clout of Iran, a Syrian government ally.
The Israeli military said earlier on Tuesday that it had no reaction, saying it does not comment on "foreign reports".
France denied any involvement in the plane's disappearance.
Russian military spokesman Igor Konashenkov said the Israeli pilots used the Russian plane as a cover to make it a target for the Syrian air defense systems.
The deal marked a significant agreement between the two leaders and effectively delays an offensive by Syria and its Russian and Iranian allies, one that Turkey fears would create a humanitarian crisis near its border.
The jet vanished from radar just hours after Russian Federation said there would be no assault against Syria's Idlib as the presidents of Russian Federation and Turkey agreed to create a "demilitarised zone" in the militant-held province. Almost half an hour later, it said the strikes continued.
Putin told a press conference that the agreement provided for the withdrawal from Idlib of "all radical fighters", including Al Nusra, and the removal from the demilitarized zone of all "heavy weaponry".
Earlier in the day, Russian Federation and Turkeyreached an agreement over a partial demilitarization of the Idlib province, which is the last remaining stronghold of anti-government insurgency and al-Qaeda-linked terror groups in Syria.
Russian Federation also announced it had lost contact with an IL-20 aircraft carrying 14 service members.