Russia's defense ministry, in a statement reported by Russian news agencies, said the Il-20 reconnaissance aircraft was brought down by anti-aircraft batteries of Moscow's ally, Syria, in a friendly fire incident.
Foreign powers involved in the conflict - including Israel and Russian Federation - operate hotlines which they use to exchange operational details to avoid one side accidentally attacking the other's forces.
"We consider these provocative actions by Israel as hostile".
"We reserve the right to take commensurate measures in response", Konashenkov was quoted as saying.
This story is being updated.
A United States official told Reuters that the plane, used for reconnaissance, was inadvertently downed by anti-aircraft...
A search operation has been launched from the Russian Hmeymim airbase which has been at the heart of Moscow's hugely effective air support of forces loyal to Syrian president Bashar al-Assad.
Israel's military declined to comment.
The ministry specified that "the mark of IL-20 went off the radars disappeared during the attack of four Israeli F-16 aircraft on Syrian targets in the province of Latakia".
Who is responsible for shooting down the Russian plane over Syria?
The plane was 35 kilometers off the coast of Syria when it went off the radars, RT quoted the Russian defense ministry as saying. RIA Novosti news agency, citing a security source, said that Syrian anti-defense systems had countered a rocket attack.
The Ministry of Defence said 15 Russian military service people had died because of what it described as Israel's irresponsible actions.
According to the CNN, the Il-20aircraft with multiple personnel on board was inadvertently shot down by Syrian regime anti-aircraft artillery on Monday after the Syrians came under attack by Israeli missiles, according to a USA official with knowledge of the incident.
In a statement to Business Insider, a US Central Command spokesman did not comment on where the strikes originated from but denied US forces were involved.
Damascus skies erupt with surface-to-air missile fire as the U.S. launches an attack on Syria targeting different parts of the Syrian capital, April 14, 2018.
A pro-government Syrian newspaper says the agreement reached between Russian Federation and Turkey over the northwestern rebel-held Syrian province of Idlib envisions three stages in returning Damascus government institutions to the area.
A Russian military jet is believed to have been inadvertently shot down in Syria.
Almost half an hour later, it said the strikes continued.
Russian Federation intervened militarily in Syria's conflict three years ago, and is one of President Bashar al-Assad's strongest allies.
Moscow has previously lost aircraft during its Syria campaign.
In November 2015, Turkey shot down a Russian warplane near the Syrian border, triggering a severe crisis in ties with Moscow.