Shortly after Syria and its principal allies, Iran and Russia, blamed Israel for bombing a major air base in central Syria on Monday, Iran's Tasnim news agency reported that seven Iranian military personnel had been killed in the strike, nearly doubling the initial report of four Iranian casualties.
Israel has not commented on the strike, which killed at least 14 people, but Israeli officials said the Tiyas, or T4, air base near Homs was being used by troops from Iran, and that Israel would not tolerate a permanent Iranian military presence in Syria.
On Tuesday, the top adviser to Iranian Supreme Leader Ali Khamenei described the strike as "Israel's crime" and said that it "will not remain without response," the Lebanese al-Mayadeen channel reported.
The adviser, Ali Akbar Velayati, made the remarks upon arriving in the Syrian capital Damascus, reported al-Mayadeen, which is well connected in government-held parts of Syria.
Also Tuesday, a top Russian diplomat said the Israeli ambassador in Moscow had been summoned by the Foreign Ministry to discuss developments in Syria following the airstrike.
Mikhail Bogdanov, Russian presidential envoy to the Middle East and Africa, told Russian news agencies on Tuesday that the Israeli ambassador to Moscow was asked to come to the Foreign Ministry "to talk" later in the day.
Asked if it was about the airstrike, Bogdanov only said Russian diplomats wanted to talk about various issues related to the Syrian war, as well as bilateral relations.
Meanwhile, Iran's state-run television quoted Iranian Foreign Ministry spokesman Bahram Ghasemi as saying the attack was a "violation of national sovereignty and the territorial integrity of this country, and contrary to all international rules and regulations."
The Revolutionary Guards, Iran's most powerful military force, have been fighting in support of Syrian President Bashar Assad for several years. More than 1,000 Iranians have been killed in Syria, including senior members of the Guards.
According to reports in Iran, Col. Mehdi Dehghan, a senior member of the Iranian Revolutionary Guards' aerospace force, which operates drones, is among the dead. One report, which named four of the Iranian casualties, raised the possibility that Iran was investing efforts into rehabilitating its drone capabilities in Syria, which could be used to target Israel in addition to Syrian rebels.
Iran's semi-official Fars news agency described the casualties as "defenders of the shrine." Iran calls its fighters in Syria the defenders of the shrine as it says they are there to protect the Zeinab Shrine, a Shiite holy site near Damascus.
The strike occurred hours after U.S. President Donald Trump warned that there would be a "big price to pay" following reports of a poison gas attack on the Syrian rebel-held town of Douma, near Damascus. Syria's government has denied using chemical weapons on civilians.
"It seems the U.S. government is looking for an excuse for military intervention. Iran's stance on chemical weapons is clear and we condemn any use of them against any target," Iranian Foreign Minister Mohammad Javad Zarif said, as he arrived in Brazil early Tuesday.
Israel said in February it had intercepted an Iranian drone launched from Syria, and it carried out airstrikes against Iranian targets in the country. At the time, Iran denied its drone had been downed in Israel.
The British-based Syrian Observatory for Human Rights said at least 14 people were killed in Sunday's raid, including some fighters of various nationalities.
The attack took place hours after U.S. President Donald Trump warned of a "big price to pay" following the reports of a poison gas attack on the rebel-held town of Douma, which killed dozens of people, including children.
