A war monitor reports on Wednesday said U.S. forces, positioned along with their Syrian Kurdish allies in eastern Syria, are on alert following the overnight Iranian missile attacks in neighbouring Iraq.
Iran fired over a dozen ballistic missiles at two bases hosting U.S. forces in Iraq, the Pentagon said, in what Tehran said was revenge for the killing of top Iranian commander Qassem Soleimani.
Mr Soleimani was killed in a U.S. drone strike near Baghdad airport last week.
The Syrian Observatory for Human Rights said U.S. forces were conducting heavy patrols near the Koniko oil field north-east of Deir al-Zour in eastern Syria.
Militiamen from the U.S. backed Kurdish Syrian Democratic Forces (SDF) were also seen atop armoured vehicles with missile launchers also patrolling the area, the Britain-based monitor added.
The watchdog, which has been covering violence in Syria since the pro-democracy uprising started there in 2011, said U.S. drones were constantly hovering over the area of the Euphrates River and monitoring the situation.
The number of U.S. soldiers in war-torn Syria is not clear.
But, the observatory head, Rami Abdel-Rahman said “only hundreds are left in Syria.”