The United States has carried out strikes on two facilities in eastern Syria used by Iran’s Islamic Revolutionary Guard Corps and affiliated groups in response to a recent series of attacks against American personnel based in Iraq and Syria by Tehran-backed militias, US Defense Secretary Lloyd Austin said Thursday.

US bases and personnel in the Middle East have been targeted in a slew of drone and missile attacks since October 17.

In assaults that used drones to target al-Asad Airbase in Iraq and al-Tanf Garrison in Syria, an American contractor for the US military died from a cardiac arrest while sheltering during one of the strikes and 21 US soldiers were lightly injured before returning to duty shortly thereafter, the Pentagon said.

US President Joe Biden “directed today’s action to make clear that the United States will not tolerate such attacks and will defend itself, its personnel, and its interests,” Austin said in a statement.

Austin stressed that the US “does not seek conflict and has no intention nor desire to engage in further hostilities, but these Iranian-backed attacks against US forces are unacceptable and must stop.”

US Secretary of Defense Lloyd Austin at the Pentagon, in Washington, October 19, 2023. (Cliff Owen/AP)

“These narrowly tailored strikes in self-defense were intended solely to protect and defend US personnel in Iraq and Syria. They are separate and distinct from the ongoing conflict between Israel and Hamas, and do not constitute a shift in our approach to the Israel-Hamas conflict,” Austin clarified

“We continue to urge all state and non-state entities not to take action that would escalate into a broader regional conflict,” he said.

According to the Pentagon, there have now been at least 19 attacks on US bases and personnel in Iraq and Syria since Oct. 17, including three on Thursday.

A senior US military official said the precision strikes hit weapons and ammunition storage areas that were connected to the IRGC, which is a US-designated terrorist organization.

Two US F-16 fighter jets carried out the sortie on sites near the town of Boukamal near the Iraqi border, the official said.

The area is thought to be a main conduit for weapons transfers between Iran and Syria or Lebanon, via Iraq.

The official said there had been Iranian-aligned militia and IRGC personnel on the base and no civilians, but the US does not have any information yet on casualties or an assessment of damage.

The official would not say how many munitions were launched by the F-16s.

Ain al-Asad air base in the western Anbar desert, Iraq, December 29, 2019. (AP /Nasser Nasser, File)

A senior defense official said the sites were chosen because the IRGC stores the types of munitions that were used in the strikes against US bases and troops.

The official told reporters that the F-16 airstrikes will have a significant impact on the ability of Iranian proxy groups to continue to attack US forces.

Asked which groups were targeted, the official said there are several that may have different names, but the US holds Tehran responsible for funding, arming, equipping and directing the proxies.

The official said the airstrikes were not designed to expand the conflict in the region but to compel Iran to direct the militia groups to cease the attacks on American bases and personnel.

The two officials briefed reporters after the strikes on condition of anonymity providing details on the mission that had not yet been made public.

Members of Iran’s Revolutionary Guard march during an annual military parade at the mausoleum of Ayatollah Khomeini, outside Tehran, Iran on September 22, 2014. (AP/Ebrahim Noroozi)

The strikes in Syria followed a direct warning Thursday from US President Joe Biden to Iran’s supreme leader Ayatollah Ali Khamenei against attacks on US troops, the White House said.

“There was a direct message relayed. That’s as far as I’m going to go,” US National Security Council spokesman John Kirby told reporters, declining to say how it was delivered.

Israel has repeatedly accused Iran of being a key force behind the coordinated Hamas attack on Israel, in which terrorists streamed across the border to carry out a devastating assault on nearby communities, which included killing some 1,400 people — mainly civilians, at taking over 220 people hostage.

However, the Biden administration has not publicly accused Iran of having a direct role in the devastating Oct. 7 attack and has said it appears so far that Tehran was not aware of it beforehand.

The US has noted that Iran has long supported Hamas and has raised concerns that Iran and its proxies could turn the conflict into a wider war.

US officials have routinely stressed that the American response is designed to be proportional, and is aimed at deterring strikes against US personnel who are focused on the fight against the Islamic State group.

While US officials have not publicly tied the recent string of attacks in Syria and Iraq to the Israel-Hamas war, Iranian officials have openly criticized the US for providing weapons to Israel that have been used to strike Gaza.

The Pentagon, meanwhile, has also beefed up air defenses in the region to protect US forces. Israel has reportedly agreed to delay its Gaza ground operation until the systems are in place.

The US has said it is sending several batteries of Patriot missile systems, a Terminal High Altitude Area Defense (THAAD) battery and additional fighter jets.

File: The US Army unloads a THAAD missile defense system in Israel, March 2019. (US Army Europe)

The THAAD is being sent from Fort Bliss, Texas, and the Patriot batteries are from Fort Liberty in North Carolina and Fort Sill in Oklahoma. An Avenger air defense system from Fort Liberty is also being sent.

Officials have said as many as two battalions of Patriots are being deployed. A battalion can include at least three Patriot batteries, which each have six to eight launchers.

US troops have also deployed or are in the process of going to the Middle East region, including those associated with the air defense systems.

The United States has already deployed two aircraft carriers to the eastern Mediterranean in a powerful show of support for Israel.

Jacob Magid contributed to this report.