Air strikes on Monday killed 18 pro-Iran fighters in east Syria, said the Syrian Observatory for Human Rights.
It was not clear who carried out the raids in the region of al-Bukamal near the border with Iraq, according to the Syrian Observatory for Human Rights.
The strikes come the same day as the Lebanese terrorist organization Hezbollah claims to have downed an Israeli drone in neighboring Lebanon amid heightened tensions in the region.
In August, the Israeli military attacked targets near Syria's capital of Damascus in what it said was a successful effort to thwart an imminent Iranian drone strike on Israel, stepping up an already heightened campaign against Iranian military activity in the region.
Iran's Islamic Revolutionary Guard Corps and Iranian proxy Hezbollah have been fighting alongside the al-Assad regime in the Syrian war.
A military media unit run by Lebanon’s Hezbollah said Israeli planes hit a Syrian army camp under construction in eastern Syria.
“The enemy targeted a camp under construction for the Syrian army and its allies to house soldiers away from civilian homes... The building was empty at the time of targeting and there were no casualties,” the media unit said, quoting a security source in Syria.
It said the incident happened in the Albu Kamal area.
The Israeli military said it does not comment on foreign reports.