The Russian Embassy in Israel on Thursday condemned the Jewish state's attack on an Iranian weapons facility in Syria earlier this week, which led to the downing of one of its military planes, as "irresponsible and "unfriendly."
Israeli efforts to alleviate tensions with Russia in the wake of the incident had appeared to be bearing fruit.
"Moscow views as irresponsible and unfriendly actions of Israeli Air Force, which exposed Russian Il-20 aircraft to danger and lead to death of 15 servicemen. Russia would take all necessary measures to eliminate threat to life and security of our military fighting against terrorism," the Russian Embassy said in a tweet.
On Tuesday, Prime Minister Benjamin Netanyahu had told Russian President Vladimir Putin that Syrian forces were to blame for the downing of the Russian military jet off Syria's coast but he offered "all necessary information" to investigate the incident.
An Israeli missile strike in Latakia, off the Syrian coast, prompted a Syrian barrage of defense missiles, one of which downed the Russian military aircraft, killing all 15 crew members, as the cargo plane was making its descent.
While initially holding Israel responsible for the deaths, Putin later said that the incident was the result of a "chain of tragic and chance circumstances" and appeared to somewhat defuse the situation, though he said Russia needed to look further into what happened.
"As for retaliatory measures, they will be aimed first and foremost at further ensuring the safety of our military personnel and facilities in Syria. And these will be steps that everyone will notice," Putin said.
Following the phone conversation, Netanyahu's office issued a statement saying that "the prime minister expressed regret on behalf of the State of Israel for the death of the Russian soldiers and said responsibility for downing the plane was placed on Syria."
It said Netanyahu emphasized the importance of defense coordination with Russia that had managed "to prevent many losses on both sides in the past three years" in Syria's civil war, where various outside powers have backed opposing forces.
Netanyahu and Putin hold frequent meetings and phone conversations and military officials communicate to ensure their respective aircraft avoid accidentally clashing in the region's airspace.
The Israel Defense Forces also expressed sorrow on Tuesday for the deaths of the crew members, but blamed Syrian President Bashar Assad and Iran.
"Israel expresses sorrow for the deaths of the aircrew members of the Russian plane that was downed ... due to Syrian anti-aircraft fire," a military statement said. "Israel holds the Assad regime, whose military shot down the Russian plane, fully responsible for this incident. Israel also holds Iran and the Hezbollah terror organization accountable for this unfortunate incident."
It said the Israeli raid late Monday night targeted a Syrian military facility where weapons manufacturing systems were "about to be transferred on behalf of Iran" to Hezbollah.
Israel also disputed Russia's assertion that it used the downed aircraft as cover while it carried out the strike.
"During the strike against the target in Latakia, the Russian plane that was then hit was not within the area of the operation. When the Syrian army launched the missiles that hit the Russian plane, [Israeli] jets were already within Israeli airspace," the IDF said in a statement.
"Extensive and inaccurate Syrian anti-aircraft fire caused the Russian plane to be hit and downed," the army added.
The United States backed Israel in the aftermath of the incident. "It sounds to me and it seems to me based on a review of the facts that Syria shot down a Russian plane," U.S. President Donald Trump said at a joint press conference with Polish President Andrzej Duda. "And I understand about 14 people were killed and that's a very sad thing but that's what happens."
Two U.S. defense officials told CNN that the target of the Israeli airstrike was likely a facility used by Iran to house sensitive military equipment that could be assembled into weapons, and then transferred to Hezbollah. The officials would not detail the intelligence that led the U.S. to this conclusion, but they pointed out a major concern of both Israel and the U.S.: that Hezbollah is gaining access to Iranian missiles that are increasingly precise and longer range in order to attack Israel.
U.S. Secretary of State Mike Pompeo said the incident underlined the "urgent need to resolve the Syrian conflict" in accordance with U.N. resolutions and "to end Iran's provocative transit of dangerous weapon systems through Syria, which are a threat to the region."
Since intervening in Syria in 2015, Russia has usually turned a blind eye to Israeli attacks. Israeli officials said recently that Israel has carried out about 200 such raids, often targeting Iran or Hezbollah, both close allies of the Syrian government, over the last two years.
Netanyahu said Israel was "determined to halt Iran's military entrenchment in Syria and the attempts ... to transfer to Hezbollah lethal weaponry [to be used] against Israel."
Israeli Air Force chief Maj. Gen. Amikam Norkin headed to Moscow on Thursday with a delegation of Israeli defense officials to present Israel's findings on the incident.
Norkin and other senior officers were expected to "present the situation report of the event regarding all aspects, including the pre-mission information and the findings of the IDF inquiry," the army said.
Moscow said its plane disappeared from the radar as it came in to land at the Hmeimim Air Base in western Syria late Monday.
The Russian Defense Ministry asserted that Israeli F-16 jets carrying out airstrikes used the Russian plane as cover to allow them to approach their targets on the ground without being hit by Syrian fire.
"Hiding behind the Russian aircraft, the Israeli pilots put it in the line of fire of Syrian anti-aircraft systems. As a result, the Ilyushin 20 ... was shot down by the [Syrian] S-200 missile system," the ministry said.
He said the Israeli pilots "could not have failed to see the Russian aircraft, as it was coming in to land from a height of 5 kilometers [3 miles]. Nevertheless, they deliberately carried out this provocation. This absolutely does not correspond to the spirit of Russian-Israeli partnership."
Meanwhile, unconfirmed reports from Syria on Wednesday said the commanders of the Syrian anti-aircraft unit that shot down the Russian plane had been arrested. According to some reports, Russian military police took part in the arrests and was questioning the Syrian officers.
