TEL AVIV – The airstrike on Syria attributed to Israel targeted an air base built by Iran and with the knowledge of Russia, constituting the “most significant direct attack” to date, Israel’s Channel 10 reported on Tuesday night.

“All the signs are that Iran was trying to build an air base in Syria,” the TV report said, according to a translation by The Times of Israel.

The Iranians will retaliate “almost certainly from Syria,” the report said. Despite the pretense of innocence, Russia almost certainly was aware of the Iranian base, the report said. The report quoted Arab sources as saying that Russia may boost the Assad regime defense for future attacks from Israel.

Iran had lost “a significant asset” and maybe “even an entire system” in the strike, the report said.

According to a separate report by Channel 2, the strike targeted a type of “advanced systems” that would make it more difficult for the Israeli Air Force to operate in Lebanese and Syrian skies.

Monday’s strike left at least 14 people dead, including 7 Iranian military personnel. Footage of the Iranian bodies arriving back in Iran to crowds chanting “Death to Israel” was shown on Israeli TV.

Former defense minister Ehud Barak told Channel 2 that an all-out conflict on the northern border was ten times more likely than in other years but that Israel’s home front was not adequately prepared for such a scenario.

The IDF on has been put on high alert after Iran threatened to retaliate for the airstrike.

Ali Akbar Velayati, a senior adviser to Iran’s Supreme Leader Ali Khamenei, called it “Israel’s crime” and said it would “not remain without response”, the Lebanese al-Mayadeen channel reported.

As well as Iran, Russia, Syria, and the U.S. all said Israel carried out the strike on the T-4 Air Base near Palmyra. Jerusalem has not confirmed the charge.

President Donald Trump on Wednesday warned Russia to “get ready” because “nice and new” missiles would be targeting Syria. Trump also slammed the Russians for allying themselves with a “Gas Killing Animal,” in reference to Saturday’s toxic gas attack in Douma which saw 42 people killed and many others gasping for breath and foaming at the mouth. Both Syria and Russia denied the attack took place.

“Russia vows to shoot down any and all missiles fired at Syria,” Trump tweeted. “Get ready Russia, because they will be coming, nice and new and ‘smart!’ You shouldn’t be partners with a Gas Killing Animal who kills his people and enjoys it!”

Within an hour, Trump tweeted again: “Our relationship with Russia is worse now than it has ever been, and that includes the Cold War. There is no reason for this. Russia needs us to help with their economy, something that would be very easy to do, and we need all nations to work together. Stop the arms race?”

Moscow responded by saying that it would view a U.S. airstrike on Syria as a “war crime.”

Russia’s foreign ministry spokeswoman Maria Zakharova said the U.S. should target “terrorists” in Syria as opposed to its “legitimate government.”

“Smart rockets should be aimed at terrorists, rather than the legitimate government, which has for several years been fighting international terrorism on its territory,” Zakharova said in a Facebook post.

The U.S. has consulted with allies to coordinate a joint response to Syria’s alleged chemical weapons attack.

French President Emmanuel Macron on Wednesday called for a “strong and joint response” to the attack.

Syria responded to Trump’s threats by evacuating airports and military airbases, the Syrian Observatory for Human Rights said.

Iran’s Foreign Ministry said Israel was responsible for “flagrant” aggression in Syria.

On Tuesday, Defense Minister Avigdor Liberman said he “didn’t know what happened” with regards to who was responsible for the attack but reiterated that Israel “will not allow Iranian entrenchment in Syria. Whatever the cost.”

“Accepting Iranian entrenchment in Syria would be to accept Iranians putting a chokehold on us. We cannot allow that,” Liberman said.