At least 18 pro-government fighters were on Monday killed in eastern Syria by airstrikes, a war monitor reported.
Unknown warplanes carried out airstrikes against Iranian-run military bases and weapon depots in the Al-Bukamal city and nearby areas in the eastern countryside of Deir al-Zour province in eastern Syria close to the Iraqi border.
The Syrian Observatory for Human Rights said the slain fighters were Iranians and allied fighters, adding that the warplanes were yet to be identified.
The UK-based watchdog group said the death toll could likely rise due to the number of critically wounded fighters.
Meanwhile, the state-run media outlets in Syria were yet to comment on the reports emerging about the airstrikes in eastern Syria.
In June of 2018, Israeli airstrikes killed 55 Iranian and pro-Iranian fighters close to Al-Bukamal.
It would be recalled that Iranian military advisors and fighters of the Lebanese Hezbollah group had military posts in eastern Syria.
However, the Lebanese Hezbollah group announced shooting down an Israeli drone over southern Lebanon earlier after crossing the border toward the southern Lebanese town of Ramyah.
The incidents were the latest escalation between the Iranian-backed fighters and Israel as Hezbollah had, in recent time, destroyed Israeli drones over Lebanon.
However, Israel considered Iran its arch-foe and had carried out hundreds of deadly airstrikes in Syria, charging the attacks target Iranian sites and weapons convoys to Hezbollah.