After spotting "several launch sites of indirect fire rockets that posed an imminent threat," coalition forces "conducted strikes to eliminate the threat," a coalition official said in a statement.

The rockets were aimed at a US base called "Green Village" in the Euphrates Valley where fighters from the Islamic State group are still active and where US forces continue to cooperate alongside the Syrian Democratic Forces (SDF).

"Indirect fire attacks pose a serious threat to innocent civilians because of their lack of discrimination" and the coalition "reserves the right to defend itself" added the official.

Asked about who might be behind the attack, the third in less than 48 hours in the region after others targeting the Ain Al-Assad air base on Tuesday in western Iraq and Baghdad international airport on Monday, Pentagon spokesman John Kirby said he could not identify them.

"I'm not in a position now to get into specific attribution," he said. "That said, we continue to see threats against our forces in Iraq and Syria by militia groups that are backed by Iran."

None of the attacks resulted in casualties, but came as Iraq marked the second anniversary of the US assassination of Soleimani, the architect of Iranian strategy in the Middle East, and his Iraqi lieutenant, killed by drone fire in Iraq on January 3, 2020.

Some 900 US troops remain deployed in northeastern Syria and at the Al-Tanf base in the south, on the borders of Iraq and Jordan.