Warplanes have struck positions of Iran-backed militias near Syria’s border with Iraq, activists say.
The Syrian Observatory for Human Rights, a UK-based monitoring group, said at least 18 Iranian and pro-Iranian fighters were killed.
It was not clear who carried out the strikes early on Monday in al-Hizam al-Akhdar, near the town of Albu Kamal.
But Israel has carried out hundreds of attacks on Iranian-linked targets in Syria during the country’s civil war.
It has sought to thwart what it calls Iran’s “military entrenchment” in Syria and shipments of Iranian weapons to militant groups such as Hezbollah in Lebanon.
Hours after the incident in Albu Kamal, a number of rockets were launched towards Israel from the outskirts of the Syrian capital, Damascus, but failed to hit Israeli territory, according to the Israeli military.
It blamed militia fighters operating under the command of the Iranian Revolutionary Guards’ Quds Force, but said it held the Syrian government responsible.
Meanwhile, Hezbollah said its fighters had shot down an unmanned Israeli drone over southern Lebanon early on Monday and seized it.
The Israeli military said one of its drones “fell inside southern Lebanon during routine operations”. It did not give a reason, but said there was “no concern information could be taken from it”.