WASHINGTON, United States - The US military carried out strikes on three sites used by Iran-backed forces in Iraq on Monday after an attack wounded three American personnel earlier in the day, Defense Secretary Lloyd Austin said.

Washington has repeatedly targeted sites used by Iran and its proxy forces in Iraq and Syria in response to dozens of attacks on American and allied forces in the region since the October 7 outbreak of the Israel-Hamas war.

"US military forces conducted necessary and proportionate strikes on three facilities used by Kataeb Hezbollah and affiliated groups in Iraq," Austin said in a statement.

"These precision strikes are a response to a series of attacks against US personnel in Iraq and Syria by Iranian-sponsored militias, including an attack by Iran-affiliated Kataeb Hezbollah and affiliated groups on Arbil Air Base earlier today," he said.

That attack wounded three US military personnel, one critically, US National Security Council spokesperson Adrienne Watson said in a statement.

President Joe Biden was briefed on the attack -- which was carried out with a one-way attack drone -- and directed the strikes in a call with Austin and other national security officials after ordering the Defense Department to prepare a response, the statement said.

- More than 100 attacks -

Biden "places no higher priority than the protection of American personnel serving in harm's way. The United States will act at a time and in a manner of our choosing should these attacks continue," the statement added.

The drone attack was claimed by the Islamic Resistance in Iraq, a loose formation of armed groups affiliated with the Hashed al-Shaabi coalition of former paramilitaries that are now integrated into Iraq's regular armed forces.

A tally by US military officials has counted 103 attacks against its troops in Iraq and Syria since October 17, most of which have been claimed by the Islamic Resistance in Iraq, which opposes US support for Israel in its war against Hamas in the Gaza Strip.

The latest round of the Israel-Hamas conflict began when the Palestinian militant group carried out a shock cross-border attack from Gaza on October 7 that killed about 1,140 people, mostly civilians according to an AFP tally based on Israeli figures.

Following the attack, the United States rushed military aid to Israel, which has carried out a relentless campaign in Gaza that has killed at least 20,670 people, also mostly civilians, according to the Hamas-run territory's health ministry.

Those deaths have sparked widespread anger in the Middle East and provided an impetus for attacks on American troops by forces opposed to their presence in the region.

There are roughly 2,500 American troops in Iraq and some 900 in Syria as part of efforts to prevent a resurgence of the Islamic State group.

The militants once held significant territory in both countries but were pushed back by local ground forces supported by international air strikes in a bloody, multi-year conflict.