Explosions were heard in eastern on Wednesday near a base belonging to the US-led international coalition against the so-called group.
Ten explosions were heard near the base, located in the , Deir az-Zour province, sources told °®Âþµº's Arabic sister service, Al-Araby Al-Jadeed.
Rocket and artillery shell fire was then heard coming from the base toward an area controlled by the Syrian regime and pro-Iran militias, the sources said.
No one has claimed responsibility for the suspected rocket fire, and there are no known casualties.
On Tuesday evening, four-armed drones struck a training camp used by Iran-aligned militias in eastern Deir az-Zour.
Other outlets reported the bombing of rocket launch sites in Deir az-Zour by the international coalition on Tuesday. A release was reportedly issued later day by the US.
The locations were set to be used to target the US-operated Green Village base, according to officials on Tuesday, the Military Times reported.
The coalition's release gave little information but did say the rocket locations "posed an imminent threat in the vicinity of Green Village, Syria".
John Kirby, spokesperson for the US Department of Defence, denied that US airstrikes had been launched and did not comment further on the suspected US shelling of the Iranian bases.
He went on to explain that "[o]ne of the reasons" for bombing the locations was "we had reason to believe" they would be used for targeting Green Village.
"So clearly our men and women remain in harm's way and we have to take that threat seriously and we always have the right of self defence," Kirby added.
Pro-Iran militias also conducted raids and arrested over 20 people in Al-Bukamal districts, Al-Araby Al-Jadeed reported local sources as saying.
The detainees were accused of communicating with the Kurdish-dominated Syrian Democratic Forces and the US-led international coalition, the sources said.
Syrian regime and Iranian militias are known to have committed various abuses - such as enforced disappearances and torture - against civilians.