On Sunday, five Iran-backed fighters were killed in an airstrike in eastern Syria near the border with Iraq the Syrian Observatory for Human Rights (SOHR), a U.K.-based war monitor reported.

The head of SOHR, Rami Abdul Rahman said that the airstrike targeted three military vehicles belonging to Iran-backed paramilitary fighters near the Iraqi border town of Albu Kamal. The Observatory said that military reinforcements for Iranian militias and their allies had arrived in the area just days before.

While the Observatory did not specifically state who conducted the airstrike, Rahman said that, “Israel was likely responsible.”

Sky News Arabia had earlier reported that unidentified aircraft carried out the pre-dawn airstrike and that the targets of the bombing were Iranian-backed proxy forces.

Iranian-backed proxy militias and their allies have a significant presence in eastern Syria south of the Euphrates Valley. They have been frequent targets of airstrikes, most of which are linked to the Israeli air force. 

Since the start of the Syrian civil war in 2011, the Israelis have launched hundreds of airstrikes in Syria, targeting Iranian Quds forces, Lebanese Shiite terror group Hezbollah forces, and Syrian troops loyal to the Assad government.

The Israeli government rarely comments on details of its operations in Syria, especially on details of airstrikes, but has in the past confirmed many of the airstrikes attributed to it. However, in this case, Israel have not yet commented. The official Israeli stance has been that Iran’s presence in support of President Bashar Assad is a threat and that it will not tolerate any Iranian bases or troop concentrations near its borders. It has vowed to continue its strikes.

Danny Dannon, the Israeli envoy to the United Nations, said in an interview that Israeli will not repeat past mistakes with Lebanon or allow Iranian bases on the Golan Heights. “We look at what happened in Lebanon and we don’t want to repeat the same mistakes we made there. So we are very determined.” He added that, “Israel would strike whenever it received intelligence that an Iranian shipment was in Syria.”

There have been several reports of suspected Israeli strikes inside Syria in the past month, including one on May 4 that left, according to SOHR, 14 Iranian-backed fighters dead.

Earlier in May, SOHR reported that airstrikes near Albu Kamal killed seven other Iranian proxy fighters on a base controlled by Tehran-backed forces. The Israeli Defense Forces (IDF), have been reporting that the Iranians are gradually withdrawing their forces from Syria due to the increased targeting of their proxy forces.

However, others have denied that the Iranians are withdrawing their proxies. Instead, about a month ago, there were other reports that the Iranians have been trying to shift their forces around the country due to the airstrikes decimating their proxies. Local news source Deir El-Zour24 reported that the Liwa Fatemiyoun and Brigade 313 militias were transferred out of the Deir El-Zour area of eastern Syria. The militias were transferred on civilian buses without weapons or escorts as to not draw attention from Israeli air force aircraft.

Omar Abu Laila, a Europe-based activist from Syria’s Deir el-Zour province, confirmed that a strike hit Iran-backed Iraqi fighters in the area, but had no exact count on any casualties.

Brigade 313 was established by the Iranian Revolutionary Guards Corps (IRGC) in southern Syria. The Fatemiyoun is a group of Afghan Shi’ites recruited by Iran’s IRGC to fight in Syria on the side of the Assad’s regime.