(FILES) In this file photo a US Bradley Fighting Vehicle (BFV) fires an AGM-114 Hellfire during a heavy-weaponry military exercise in the countryside of Deir Ezzor in northeastern Syria, on March 25, 2022. - US President Joe Biden on August 23 ordered air strikes in eastern Syria targeting facilities used by Iranian-backed militias, a US military spokesman said. The strikes in oil-rich Deir Ezzor province "targeted infrastructure facilities used by groups affiliated with Iran's Islamic Revolutionary Guard Corps". (Photo by Delil SOULEIMAN / AFP)

Within 24 hours, the US Air Force once again bombed positions of militias loyal to Iran in the east of civil war-torn Syria. Three militiamen were killed, the Syrian Observatory for Human Rights reported on Thursday.

The US Central Command also spoke of two or three dead. The bombings were said to have been in response to coordinated militia missile attacks on two US Army facilities in the region shortly before.

US Department of Defense spokesman Patrick Ryder said in Washington on Thursday that another militia fighter had been killed in another operation. This increases the death toll to four.

According to its own statements, the United States had already attacked positions of Iranian militias in the eastern Syrian province of Dair as-Saur on Wednesday night. According to human rights monitors, six militia fighters were killed.

Pentagon top official Colin Kahl said on Wednesday that the attack was necessary to protect US troops in the region. The US soldiers had been fired on several times by the militias. “This operation demonstrates that the United States will not hesitate to defend itself against Iranian and Iranian-backed aggression,” Kahl said.

Pentagon spokesman Ryder said the groups were testing how far they could go and how the US would respond. “And I think that with our attacks we sent a very loud and clear message and a proportionate message that any threat to our forces in Syria or anywhere else will not be tolerated.” It is hoped that such militia attacks will not be repeated.

While negotiations on a new nuclear deal with Iran are sluggish, Syria and neighboring Iraq have become a theater of conflict between Washington and Tehran. Iran is a close ally of ruler Bashar al-Assad in the Syrian civil war.