BAGHDAD, Nov 21 (Reuters) - U.S. forces were attacked at Ain al-Asad air base, west of Baghdad, on Tuesday, resulting in injuries and minor infrastructure damage, according to two U.S. officials. In self-defense, a U.S. military aircraft fired upon Iranian-backed militants, killing a number of them.

The attack on Ain al-Asad air base was carried out using a close-range ballistic missile, leading to eight injuries and slight damage to the base's infrastructure. The United States retaliated by deploying an AC-130 aircraft that was already in the air. The aircraft targeted a vehicle belonging to an Iranian-backed militia group, as well as several individuals involved in the attack, confirmed Sabrina Singh, a spokesperson for the Pentagon.

This incident marks the first public retaliation on Iraqi territory in response to recent attacks by militant drones and missiles on U.S. troops. However, Singh noted that there have been previous responses that were not publicly announced.

Until now, the United States had limited its response to the 66 attacks carried out against its forces in Iraq and neighboring Syria, attributed to Iraqi militia groups aligned with Iran. This response represents a departure from the previously conducted three separate sets of strikes in Syria.

Since October 17, there have been a series of attacks linked by Iraqi militia groups to U.S. support for Israel during the Gaza conflict, sparked by attacks from Palestinian militant group Hamas. At least 62 U.S. personnel have sustained minor injuries or traumatic brain injuries as a result of these attacks.

The attacks against U.S. targets have brought an end to a year-long unilateral truce that various Iraqi factions, some formed after the 2003 U.S. invasion, and others established in 2014 to counter the Islamic State, had declared with Washington.

Social media accounts associated with Iranian-aligned Iraqi militias released a statement on behalf of the "Islamic Resistance in Iraq," mourning the loss of a member during the battle against U.S. forces on Tuesday. No further details were provided regarding the circumstances of the member's death.

This reported casualty in Iraq is the first to be linked to the ongoing conflict in Gaza. The situation has drawn the involvement of other factions within Iran's network of regional militias, such as Lebanon's Hezbollah, collectively known as the Axis of Resistance.

The United States currently maintains 900 troops in Syria and 2,500 in Iraq with the mission of advising and assisting local forces in preventing a resurgence of the Islamic State, which had captured significant territories in both countries in 2014 before being defeated.