Washington: The United States, for the second time in recent weeks, carried out strikes on Wednesday against a weapon storage facility in eastern Syria that the Pentagon said was used by Iran's Islamic Revolutionary Guard Corps (IRGC) and affiliated groups.

As tensions soar over the Israel-Hamas conflict, US and coalition troops have been attacked at least 40 times in Iraq and Syria by Iran-backed forces since the start of October. Forty-five US troops have suffered traumatic brain injuries or minor wounds.

In a statement, US Defense Secretary Lloyd Austin said the strikes were conducted by two US F-15 fighters and were in response to the recent attacks against US forces.

Austin said the attacks against US troops must stop.

"If attacks by Iran's proxies against US forces continue, we will not hesitate to take further necessary measures to protect our people," Austin added.

The United States has occasionally carried out retaliatory strikes against Iranian-backed forces in the region after they attack American forces.

On October 26, US forces attacked two facilities used by the IRGC and groups its backs.

The United States has 900 troops in Syria, and 2,500 more in neighboring Iraq, on a mission to advise and assist local forces trying to prevent a resurgence of Islamic State, which in 2014 seized large swathes of both countries but was later defeated.

There is growing concern that the Israel-Hamas conflict could spread through the Middle East and turn US troops at isolated bases into targets.

Earlier on Wednesday, a US MQ-9 drone was shot down near Yemen by the Iran-aligned Houthi movement.

The United States has sent warships and fighter aircraft to the region since the Israel-Hamas conflict erupted on October 7, including two aircraft carriers, to try to deter Iran and Iran-backed groups. The number of troops added to the region is in the thousands.

Reuters has reported that the US military was taking new measures to protect its Middle East forces during the ramp-up in attacks by suspected Iran-backed groups, and was leaving open the possibility of evacuating military families if needed.

The measures include increasing US military patrols, restricting access to base facilities and boosting intelligence collection, including through drone and other surveillance operations, officials say.