The US military launched airstrikes on two sites in eastern Syria linked to Iran’s Revolutionary Guard Corps, the Pentagon said, amid growing fears that the war between Israel and Hamas could escalate into a regional conflict.

The attacks hit an arms storage facility and an ammunition storage facility used by the Revolutionary Guards and the militia, senior US officials told Reuters, noting that it was unclear whether any Iranian nationals were killed.

The strikes occurred at about 4:30 a.m. Friday near Abu Kamal, a Syrian town on the border with Iraq, and were carried out by two F-16 fighter jets using precision munitions, one of the officials said.

US Secretary of Defense Lloyd Austin announced that the “precision strikes”, in “legitimate defense”, are “in response to a series of ongoing and mostly unsuccessful attacks against US (including military) personnel in Iraq and Syria by paramilitary groups supported by Iran’ after 17 October.

He clarified that they were done by order of President Joe Biden.

The operations were announced following Biden’s message to Iran’s Supreme Leader Ayatollah Ali Khamenei, warning him against any attack on US troops, amid heightened concerns about the spread of the war between Israel and Hamas.

“He was given a clear message. I will not go further,” confirmed the representative of the national security council of the American presidency, John Kirby.

According to the Pentagon, a US citizen succumbed to cardiac arrest while taking cover during one of the attacks. Another 21 suffered minor injuries but have since returned to duty.

President Biden ordered the strikes “to make it clear that the US will not tolerate such attacks and will defend itself, its personnel and its interests,” according to Mr. Austin.

The strikes are “separate from the ongoing conflict between Israel and Hamas” and do not signal “a change in our approach” to this war, the defense minister added.

Earlier yesterday, the Pentagon announced that US forces and their allies had been the target of at least 16 attacks in Syria and Iraq (12 and 4 respectively) since the beginning of the month, again blaming “paramilitary groups linked to Iran”.

Armed groups close to Iran have threatened to attack US bases over US support for Israel, which declared war on Hamas after the Palestinian Islamist movement’s unprecedented attack on Israeli territory on October 7.

Last Wednesday, Ayatollah Khamenei accused the US of somehow “directing” Israel’s war against Hamas. On the same day, US President Biden issued a warning to Tehran against any attack against US armed forces. “My warning to the ayatollah is that if (the Iranians) continue to act against our troops, we will retaliate, and they must be ready. This has nothing to do with Israel.”

US Defense Secretary Austin said that if the “unacceptable” attacks “by Iran and its intermediaries” continue, Washington “will not hesitate” to retaliate against them again.

Washington has about 900 troops deployed in Syria and nearly 2,500 more in Iraq as part of operations against the Islamic State group.