TEL AVIV – Russia supplied Syria with three S-300 anti-aircraft battalion sets with eight launchers and more than 100 surface-to-air guided missiles each free of charge, Russia’s state news agency TASS reported.

“On October 1, three battalion sets of S-300PM systems of eight launchers each were delivered to Syria,” a military source told TASS.

“These systems were previously deployed at one of the Russian aerospace forces’ regiments which now uses the S-400 Triumf systems. The S-300 systems underwent capital repairs at Russian defense enterprises, are in good condition and are capable of performing combat tasks,” he said.

The source added that the systems were provided for no money, contradicting an earlier report by Israel’s Kan broadcaster that said Syria paid a billion dollars for the system.

U.S. National Security Adviser John Bolton last month warned that the deployment of the S-300 would overturn Syrian skies, which regularly see warplanes from Russia, Israel and the U.S.-led coalition against the Islamic State.

Russian Defense Minister Sergei Shoigu first confirmed the S-300’s delivery during a meeting with President Vladimir Putin which was broadcast by Rossiya 24 TV.

The system will improve the security of Russian military personnel in Syria, Shoigu said, echoing Russian Foreign Minister Sergei Lavrov’s words at a UN press conference the week before.

Russia was “devoted to [ensuring] 100 percent safety and security of our men in Syria,” Lavrov said.

The battalion sets will challenge Israel’s ability to target Iranian sites in Syria. Each battery has a radius of some 125 miles. As such, the decision to supply the S-300s to Syria was strongly criticized by Jerusalem.

“The S-300 is a complex challenge for the State of Israel. We are dealing with the [decision] in different ways, not necessarily by preventing shipment [of the anti-aircraft system],” an Israeli official said.

Russia transported the air defense systems to Syria using the Antonov An-124 Ruslan, one of the largest military planes in the world.

The giant aircraft, also known as the Condor, is the world’s second-largest aircraft after the Antonov An-225 Mriya, also Russian-made. The Ruslan, which weighs 192 tons and has a wingspan of 240 feet, was spotted by aviation enthusiasts on the Russia-Syria route.

Prime Minister Benjamin Netanyahu on Wednesday said he had told Russia’s vice premier that Moscow’s delivery of the S-300 air defense system to Syria would not deter Israel from operating against Iranian targets in Syria.

The Israeli military would continue its “legitimate activity in Syria against Iran and its proxies, which state their intention to destroy us,” Netanyahu  told Maxim Akimov during a meeting in Jerusalem the day before.

He added, however, that he was committed to repairing fraying ties between Russia and Israel following the downing of a Russian plane by Syrian air defenses during an Israeli airstrike last month, which Russia blamed on Israel.

Netanyahu last week said he expressed to Putin “our deep regret over the loss of the crew of the Russian plane that was brought down by irresponsible Syrian anti-aircraft fire.”

Netanyahu said he told Putin, “Let’s continue this deconfliction, but at the same time, I told him very respectfully and very clearly that Israel will do, will continue to do what it has to do to defend itself.”

Last Thursday, U.S. General Joseph Votel, who heads the U.S. Central Command, said the Russian S-300 delivery to Syria was a “needless escalation.”

A day before, U.S. Secretary of State Mike Pompeo described the move as a “very serious escalation.” He had previously warned Moscow that Washington would hold Russia “accountable” if it went ahead with the transfer.