The U.S. military said it carried out airstrikes on Tuesday targeting areas of eastern Syria controlled by Iran-backed militias.
The "precision strikes" in the oil-rich Deir ez-Zor province, near Syria's border with Iraq, "targeted infrastructure facilities used by groups affiliated with Iran's Islamic Revolutionary Guard Corps," according to Col. Joe Buccino, spokesman for the U.S. Central Command.
"Today's strikes were necessary to protect and defend U.S. personnel," Buccino said in a statement. "The United States took proportionate, deliberate action intended to limit the risk of escalation and minimize the risk of casualties."
Buccino did not offer any casualty numbers from the strikes.
Neither Syria nor Iran immediately acknowledged the attack.
The Syrian Observatory for Human Rights, a U.K.-based war monitoring group, said the U.S. strikes targeted the Ayash Camp run by the Fatemiyoun Brigade, a militia made up of Afghan Shiite refugees sent by Iran to fight in the ongoing Syrian Civil War alongside Syrian government troops. At least six Syrian and foreign militants were reportedly killed in the strikes, according to the Syrian Observatory for Human Rights.
According to Buccino, the strikes came at the orders of U.S. President Joe Biden in response to an attack on Aug. 15, when Iran-backed militias allegedly launched drones targeting the al-Tanf Garrison used by U.S. forces in the energy-rich Homs province in central Syria. At that time, U.S. Central Command described the attack as causing “zero casualties and no damage."
"The United States does not seek conflict, but will continue to take necessary measures to protect and defend our people," Buccino added. "U.S. forces remain in Syria to ensure the enduring defeat of ISIS."
The strikes came as Biden seeks to revive a 2015 nuclear deal with Iran that his predecessor abandoned.
Since 2014, the U.S. has led a coalition of countries conducting strikes targeting the Islamic State group in Syria. U.S. ground forces entered Syria in 2015. In more recent years, the American-led coalition has also launched strikes targeting the Syrian government's forces and allies, mainly in defense of the Syrian Democratic Forces, a U.S.-backed alliance of Kurdish and Arab militias that was formed as part of the campaign against ISIS.
What started as a local protest movement in Syria's southern city of Dara'a expanded into a full-fledged civil war by 2012. ISIS, which grew out of al-Qaeda in Iraq, took root in northern and eastern Syria in 2013 after seizing swaths of territory in neighboring Iraq. The jihadist group is fighting to overthrow Syrian President Bashar al-Assad's regime and establish a caliphate.
The Syrian Civil War has pulled in the United States, Russia, Iran and almost all of Syria's neighbors. It has become the largest humanitarian crisis since World War II, according to the United Nations.