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By Idrees Ali and Phil Stewart
WASHINGTON, Oct 26 (Reuters) - The U.S. military carried out strikes against two facilities in eastern Syria used by Iran's Islamic Revolutionary Guard Corps and groups it backs, the Pentagon said on Thursday, in response to a spate of attacks against U.S. forces in both Iraq and Syria.
As tensions soar over the Israel-Hamas conflict, U.S. and coalition troops have been attacked at least 19 times in Iraq and in Syria by Iran-backed forces in the past week.
A total of 21 U.S. forces have suffered minor injuries, the vast majority of them traumatic brain injuries.
"These precision self-defense strikes are a response to a series of ongoing and mostly unsuccessful attacks against U.S. personnel in Iraq and Syria by Iranian-backed militia groups that began on October 17," U.S. Defense Secretary Lloyd Austin said in a statement.
The strikes were ordered by President Joe Biden.
"These Iranian-backed attacks against U.S. forces are unacceptable and must stop," Austin said in the statement.
"If attacks by Iran's proxies against U.S. forces continue, we will not hesitate to take further necessary measures to protect our people."
The strikes took place at roughly 4:30 a.m. on Friday in Syria (0130 GMT) near Abu Kamal, a Syrian town on the border with Iraq, and were carried out by two F-16 fighter jets using precision munitions, a senior U.S. official, speaking on the condition of anonymity, said.
The targets were weapons and munitions storage facilities, the official added, speaking late on Thursday to reporters in Washington.
The United States has occasionally carried out retaliatory strikes against Iranian-backed forces in the region after they attack American forces. In March, the U.S. military carried out multiple air strikes in Syria against Iran-aligned groups that it blamed for a drone attack that killed an American contractor.
President Biden has sent a rare message to Iranian Supreme Leader Ayatollah Ali Khamenei warning Tehran against targeting U.S. personnel in the Middle East, the White House said earlier on Thursday.
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 U.S. troops at isolated bases into targets.