Iran-backed forces in Syria have said their response to an Israeli air strike on Palmyra in Syria would be “very cruel”.
The strike in the province of Homs on Wednesday was the second within a week.
Israel has kept silent about the strike that came only days after Damascus reported its air defences had intercepted an Israeli missile attack above the Homs countryside, which wounded six Syrian soldiers and caused material damage.
Israeli missiles flew over Jordanian airspace above US forces based in the Tanf area at the Syrian-Iraqi border, the Syrian Defence Ministry said.
Israel has been mounting attacks on what it has described as Iranian-linked targets in Syria for several years. Tehran-backed forces including Lebanon's Hezbollah have formed a presence in the country to help Syrian President Bashar Al Assad in the Syrian conflict that erupted in 2011.
A statement by the so-called operations room of his Iran-backed allies said the response to the strike would be "very cruel". It said casualties would have been much higher had its forces not been well spread across the desert area.
"As a result of this attack a number of martyrs and injured from our Mujahedeen brothers have fallen," said the statement published on pro-Iranian news outlets that Reuters verified.
"We have taken a decision to respond to this attack in revenge for the martyrs and the blood of the injured and the response will be very cruel.”
A senior military source who requested anonymity said the strikes hit, among other targets, the T4 airbase where Iran-backed militias launched drone strikes in recent months against US bases in northern Syria.
The Palmyra area where the strikes were conducted is near a major concentration of Russian bases where its troops recently conducted manoeuvres with Syrian troops, military experts say.
Israel wants Iranian and Iran-backed forces kept away from its border and more broadly, removed from Syria entirely.