The crash which killed 15 Russian service members had forced Moscow to take "adequate retaliatory measures to increase the safety of Russian military fighting international terrorism in Syria," Shoigu said in a televised address.

Russia will supply an S-300 surface-to-air missile system to Syria within two weeks, Defense Minister Sergei Shoigu said on Monday, a week after Russia blamed Israel for indirectly causing the downing of a Russian military plane in Syria.

"A modern S-300 air defence missile system will be transferred to the Syrian armed forces within two weeks," he said. The system will "significantly increase the Syrian army's combat capabilities," he said.

Russia, which fights in Syria to support the government, has said Syria shot the IL-20 surveillance plane down by mistake shortly after Israeli jets hit a nearby target. Russia blamed Israel for creating dangerous conditions that caused the crash.

Israel, which has struck Syria scores of times during the seven-year war, has said it will work to improve "deconfliction" of its missions with Russian forces, but will not halt them. It has long lobbied Moscow not to provide the S-300 to Syria.

Shoigu said Russia will equip Syrian anti-aircraft units with Russian tracking and guidance systems in order to identify Russian aircraft.

Russia in April had hinted that it would supply the S-300 to President Bashar al-Assad despite Israeli objections.

The missile system, originally developed by the Soviet military, but since modernized and available in several versions with significantly different capabilities, fires missiles from trucks and is designed to shoot down military aircraft and short- and medium-range ballistic missiles.

Israel says its air strikes on Syria are not a threat to Russia's ally Assad, but that it must carry them out to halt arms shipments to Iranian-backed Lebanese group Hezbollah. It has made repeated efforts to persuade Moscow not to sell S-300s to Syria, as it fears this would hinder its aerial capability.