The White House had earlier warned that it would respond to attacks on its forces in Iraq and Syria.

The United States has attacked two facilities in Syria used by Iran’s Islamic Revolutionary Guard Corps and Iran-backed groups, the Pentagon has said, following a series of attacks against US forces in Iraq and Syria.

The strikes came after President Joe Biden’s administration pledged to respond to attacks on US personnel that Washington has blamed on armed groups backed by Iran.

“These precision self-defense strikes are a response to a series of ongoing and mostly unsuccessful attacks against US personnel in Iraq and Syria by Iranian-backed militia groups that began on October 17,” US Defense Secretary Lloyd Austin said in a statement on Thursday.

White House National Security Council spokesman had earlier warned that Washington would respond to the attacks at a “time of our choosing and a manner of our choosing.”

Kirby’s comments came as the US Department of Defense said on Thursday that US and allied forces in Iraq and Syria had been attacked at least 16 times this month by “Iranian-backed militia groups”.

Reported attacks on US forces in the region have spiked since the outbreak of the Israel-Hamas war, which began earlier this month when the Palestinian group launched an unprecedented attack on Israel that Israeli officials say killed more than 1,400 people.

Palestinian authorities say more than 7,000 people have been killed in Israeli air strikes on Gaza carried out in response to Hamas’s October 7 attacks.

On Wednesday, Biden said he had directly warned Iranian Supreme Leader Ayatollah Ali Khamenei against targeting US troops in the Middle East.

“My warning to the ayatollah was that if they continue to move against those troops, we will respond, and he should be prepared,” Biden told reporters, adding it has “nothing to do” with Israel.

Washington and Tehran do not have formal diplomatic relations, and Biden did not say how the message was communicated.

Mohammad Jamshidi, an aide to Iran’s President Ebrahim Raisi, disputed Biden’s account in a comment posted on social media.

“The US messages were neither directed to the leader of the Islamic Revolution nor were they anything but requests from the Iranian side,” he said.

“If Biden thinks he has warned Iran, he should ask his team to show him the text of the messages.”

US officials are concerned about the possibility of fighting between Israel and Hamas escalating into a broader regional conflict.

Iran backs both Hamas, which governs Gaza, and the Lebanese armed group Hezbollah, which Israel has clashed with in skirmishes along the Israel-Lebanon border.

On Thursday, Iran’s Foreign Minister Hossein Amir-Abdollahian said at the United Nations that the US would “not be spared from this fire” if Israel’s bombardment of Gaza did not end.

“I say frankly to the American statesmen, who are now managing the genocide in Palestine, that we do not welcome [an] expansion of the war in the region,” Amir-Abdollahian said. “But if the genocide in Gaza continues, they will not be spared from this fire.”