On Tuesday night US Central Command announced that it had "conducted precision airstrikes in Deir ez-Zor Syria" in order to "defend and protect U.S. forces from attacks like the ones on August 15 against U.S. personnel by Iran-backed groups."

"The President gave the direction for these strikes pursuant to his Article II authority to protect and defend U.S. personnel by disrupting or deterring attacks by Iran-backed groups," CENTCOM said.

Iran has denied any link to the troops targeted in the airstrikes, up to ten of whom were reportedly killed.

The US attack was followed by rocket attacks on US military positions in eastern Syria, injuring an unknown number of US troops, to which the US responded with an Apache helicopter assault on Syrian vehicles from which it claims the rockets were launched. Central Command claims "two or three suspected Iran-backed militants" were killed in the helicopter attack.