The Russian military said on Monday that two Israeli F-15 war planes carried out airstrikes on a Syrian air base near Homs on Sunday, the Interfax news agency reported. 14 people were reportedly killed in the strike, at least four of them Iranians.

Interfax cited the Russian Defense Ministry as saying the Israeli war planes had carried out the strikes from Lebanese air space. The Russian ministry said that Syrian air defense systems had shot down five of eight missiles fired, while the other three landed in the western part of the base. Russian Foreign Minister Sergei Lavrov said Monday that the strike was "a dangerous development."

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Asked about the Russian statement, an Israeli military spokesman said he had no immediate comment.

The Lebanese TV channel Al Mayadeen, which is also associated with the Assad regime, said that Moscow has demanded clarification from Israel regarding the night attack.

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Open gallery view Photos of Iranian drones and control center, released by Israel after it struck T-4 air base in Feb. Credit: IDF Spokesperson's Unit

The station quoted "Russian experts" in Syria as saying that the strike was an Israeli reaction to the understandings reached between Russia, Iran and Turkey in a summit in Ankara last week. They added that Israel was acting as the long arm of the U.S., which has not wanted to attack Syria directly in order not to provoke Russia. The sources said that the attack was coordinated between Israel and the U.S.

Twitter post by FDD's Iran Project naming four Iranian killed in strikes on T-4 air base in Syria

Iran's Fars news agency reported that four Iranians were killed in the air strike, which it attributed to Israel. Media outlets associated with the Iranian Revolutionary Guard Corps named the four dead, which included a senior officer in Iran's unmanned aerial vehicle program.

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Israel had attacked the T-4 base near Homs twice in the past, destroying an Iranian drone control center and communications systems, where defense analysts say there are large deployments of Russian forces, and where jets fly regular sorties to strike rebel-held areas.

Dmitry Peskov, spokesman for Putin, told reporters on Monday that Israel had not spoken to the president ahead of the air strike even though there may have been Russian military advisers at the base, which he described as "a cause for concern for us."

U.S. officials however told NBC news that Israel informed Washington of its plans to attack in Syria. The officials confirmed that it was the Israeli military that carried out the strike on an air base in Syria - something Israel has not officially acknowledged, as part of its policy of not directly taking responsibility for actions in the Syrian arena.

Open gallery view Russian President Vladimir Putin and Syrian counterpart Bashar al-Assad at the Kremlin in Moscow, October 21, 2015 Credit: AFP

Earlier, Syrian state TV reported casualties in what it called a suspected U.S. missile attack on the major air base in central Syria, close to the ancient city of Palmyra. The Syrian Observatory For Human Rights, a monitoring group, said that 14 people were killed, including Iranian nationals.

Rami Abdurrahman, who heads the Britain-based Syrian Observatory for Human Rights, says most of the 14 killed were either Iranians or members of Iran-backed groups.

The Lebanese army said in a statement Monday that four Israeli planes violated Lebanon's airspace, flying from the Mediterranean Sea over the coastal town of Jounieh and then heading east, toward the city of Baalbek near the Syrian border. The statement said the warplanes stayed in Lebanese airspace for about 10 minutes, starting at 3:25 A.M. before leaving it.

The army did not say whether the warplanes carried out the airstrikes on Syria's T-4 air base.

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"An aggression was perpetrated on T-4 air base in several strikes that is most likely to be an American attack," state television said in a news flash.

The U.S. Pentagon said it was not conducting airstrikes in Syria "at this time," formally denying the Syrian state television report.

Al-Manar TV station of Lebanon's Iran-backed Hezbollah group, which is fighting in Syria alongside the government forces, described the attack as an "Israeli aggression."

Israel has struck Syrian army locations many times in the course of the conflict, hitting convoys and bases of Iranian-backed militias that fight alongside Syrian President Bashar Assad's forces.

In February, Israel struck the T4 air base afte the infilitration of an Iranian drone into Israeli airspace. The strikes by Israel took out the batteries that fired missiles at its fighter jets and also hit Iranian targets, including the drone control center and communications systems. In March 2017, following another strike, Israel's Arrow system intercepted Syrian air defenses missiles that were shot at Israeli jets.

Prime Minister Benjamin Netanyahu had a "tense" phone call with U.S. President Donald Trump last week, according to two White House officials. The conversation revolved around Netanyahu's concerns that the U.S. will withdraw from Syria and allow Israel's enemies, Iran and its affiliate militias, to gain a further foothold in the neighboring country, said the officials.

A White House statement released following the call said Netanyahu and Trump spoke about "recent developments in the Middle East," and that the president "reiterated the commitment of the United States to Israel’s security and the two leaders agreed to continue their close coordination on countering Iran’s malign influence and destabilizing activities."

Trump said earlier on Sunday there would be a "big price to pay" after medical aid groups reported dozens of civilians, including many children and women, were killed by poison gas in a besieged rebel-held town.

The United States launched a cruise missile strike on a Syrian air base a year ago in response to the killing of dozens of civilians in a sarin gas attack in an opposition-held town in northwest Syria. The gas attack was blamed on Assad. The U.S. missile strike was against a Syrian air base which Washington said was used to launch the strike.

The French army said France did not stage the attack on the Syrian base, AFP reported. The denial comes following a conversation between Trump and French President Emmanuel Macron in which the two leaders agreed to "coordinate a strong, joint response" to the chemical attack in Syria.

The Syrian state denied government forces had launched any chemical attack. Russia, Assad's most powerful ally, called the reports fake.

The UN Security Council planned to hold an emergency meeting Monday to discuss the chemical attack.