USA national security adviser John Bolton meanwhile said Monday that delivery of the Russian S-300 would be a "significant escalation" in already high tensions in the region, and Secretary of State Mike Pompeo said he would raise the matter this week with his Russian counterpart Sergey Lavrov at the U.N. General Assembly. Israel said Syria was responsible.
Shoigu said S-300 missiles will strongly strengthen combat capabilities of the Syrian air defense due to their jamming invulnerability and firing speed.
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An unnamed source in the Syrian Army say that Russia has already deployed the first S-300 systems to the Khmeimim (Russian military airbase in Syria).
According to the ministry of defense, the Russian military aircraft was shot down before landing at the Hmeimim air base.
In a statement, the Israel Defense Forces maintained its version of events - that the Russian reconnaissance plane was shot down as a result of indiscriminate Syrian anti-aircraft fire - and said it would continue to act to prevent terrorist groups from obtaining advanced weapons. All Israel's "claims about its alleged noninvolvement in this tragedy that claimed lives of 15 Russian servicemen are false", he added.
In a televised address, Russian Defense Minister Sergei Shoigu said that the new system would provide "adequate retaliatory measures to increase the safety of Russian military fighting global terrorism in Syria".
But when the dust settled, blame fell on Israel.
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'Russia in this case is acting in its interests only, these actions are not directed against third countries, but towards defending our own military, ' he said.
But after the downing of the plane last week, "the situation has changed", Defense Minister Sergei Shoigu said in an address carried live on national television. "Most importantly, this will guarantee that Russian aircraft are identified by Syrian air defences", he said.
Moscow first announced that it was considering reversing its longtime policy against supplying the S-300 system to the regime following a series of airstrikes against Syrian targets by the United States, United Kingdom and France in response to an alleged chemical weapons attack by Assad.
Earlier, the Russian MoD presented a minute-by-minute timeline of the Il-20 downing.
Israel, which has struck Syria scores of times during the seven-year war, said after the incident that it would work to improve "deconfliction" of its missions with Russian forces, but would not halt them. Foreign Minister Sergei Lavrov said the strikes had removed any moral obligation Russian Federation had to withhold the missiles and Russia's Kommersant daily cited unnamed military sources as saying deliveries might begin imminently.
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