Unknown aircraft have attacked posts of Iranian-backed fighters in an eastern town near the Iraqi border, Syrian opposition activists and the Syrian Observatory for Human Rights said Tuesday.
The activists said the airstrikes took place in Boukamal, in the eastern province of Deir Ezzor.
They killed 10 pro-Iranian Iraqi militiamen, the Observatory said.
They targeted "three positions of the Revolutionary Guards and allied (Iraqi) militias," it added.
Last week, unknown warplanes targeted an arms depot and posts of Iranian-backed militias in Boukamal, killing at least 18 fighters.
A Syrian security official said Israeli jets were behind the attack but denied there were casualties.
The Britain-based Observatory and Deir Ezzor 24, an activist collective, said the strikes occurred near the border crossing with Iraq.
The opening of the crossing, planned by Iraq and Syria, had been postponed several times in recent weeks.