DAMASCUS - At least 13 pro-Iran fighters were killed in US airstrikes that targeted strongholds of pro-Iran fighters in the eastern province of Deir al-Zour on Friday night just as the US was readying retaliatory strikes against Iranian targets, a war monitor reported.

The airstrikes targeted the Haidariya region in the desert of the city of al-Mayadeen as well as the shrines of Ain Ali and Al-Shibli in the countryside of al-Mayadeen.

The strikes also targeted the al-Hizam area and the industrial neighborhood in the city of al-Bukamal near the Syrian-Iraqi border, according to the Syrian Observatory for Human Rights.

Overall, the war jets destroyed 17 sites in Deir al-Zour in three rounds of airstrikes on al-Mayadeen and one round on al-Bukamal.

US reconnaissance planes continue to patrol the region's airspace intensively, said the Observatory, adding that sources revealed significant confusion among Iran-affiliated militias due to a lack of intelligence about potential targets and their readiness to absorb the expected US strike in the coming hours.

The Observatory further said that top Iranian advisors withdrew to Damascus, while some elements of the Iranian Islamic Revolutionary Guard Corps (IRGC) remained in Deir al-Zour, with the Lebanese Hezbollah and the Fatimiyoun Brigade, both supported by the IRGC, tasked with managing the operations in Deir al-Zour.

Two hours before the US attack, the Observatory said Israeli and Western electronic intelligence and aerial surveillance planes were conducting intensive reconnaissance deep into Syrian territory, towards central and southern Syria.

Meanwhile, the state-run TV confirmed the death and injury of several "martyrs" at different attacked sites in Syria.

The US-based ABC News cited a US official as confirming that strikes in retaliation for a recent deadly attack on a US base in Jordan have begun in Syria.

On Sunday, three US servicemen were killed in a drone strike on an American base in Jordan. Pro-Iran militias, which have intensified their drone attacks on US bases in Syria and Iraq in tandem with the Israeli military campaign on Gaza, were blamed for the attack.

Israel has also upped its strikes on Iranian interests in Syria, killing many members of the IRGC members in Syria.

Earlier on Friday, Israeli warplanes conducted an aerial attack on several locations south of the Syrian capital, the Syrian Defense Ministry said in a statement.

According to the statement, the attack was launched from the direction of the occupied Syrian Golan Heights.

The Observatory said a counselor in the IRGC and an Iraqi person with him were killed in the strikes.

As tension continues to escalate in the region, the US airstrikes could be just the initial stages of a succession of targeted attacks on pro-Iran militias in Syria, as reported by the Observatory. The airstrikes have been confirmed to be ongoing.