The United States has launched air strikes in eastern Syria targeting facilities used by Iran-backed militias, the Pentagon said.

The Defense Department said on February 25 that the strikes were in response to rocket attacks earlier this month on an Iraqi base housing U.S. and coalition troops.

"The operation sends an unambiguous message: President [Joe] Biden will act to protect American and coalition personnel," the Pentagon said.

The statement said the strikes hit "multiple facilities" at a control point on the Syria-Iraq border used by several Iran-backed militias, including the Iraqi Shiite groups Kaitib Hizballah and Kaitib Sayyid al-Shuhada.

It was not immediately clear if the militia groups sustained casualties or what facilities were hit.

The Pentagon did not say whether the militia groups sustained casualties or what facilities were hit.

But the Syrian Observatory for Human Rights, a war monitor, said that 17 members of Iraq's state-affiliated Popular Mobilization Units (PMU) were killed after the strike hit three trucks loaded with munitions coming from Iraq.

The PMU is an umbrella paramilitary force composed of a number of mostly Shiite Iraqi militia groups.

The strikes come after three recent rocket attacks.

A February 15 rocket salvo on a military base at Irbil International Airport in the capital of Iraq's autonomous Kurdish region killed one civilian contractor and wounded a U.S. service member and other coalition troops.

Another rocket attack on a base hosting U.S. forces north of Baghdad days later hurt at least one contractor. Yet another rocket barrage targeted the U.S. Embassy in Baghdad earlier this week.

A little-known Shiite militant group calling itself the Guardians of Blood Brigade claimed responsibility for the attack in Irbil. Some experts say Kaitib Hizballah has used separate militant cells as a cover to absolve itself of responsibility for attacks on U.S. forces.

Under former U.S. President Donald Trump, the United States blamed Iran-backed Iraqi militia for regular rocket salvos targeting bases hosting U.S. and coalition troops as well as at the U.S. Embassy in Baghdad's Green Zone.

Tensions between Washington and Tehran escalated after Trump in January 2020 ordered a drone strike in Baghdad that killed Iran's top general, Qasem Soleimani, and Abu Mahdi al-Muhandis, the leader of Kaitib Hizballah and deputy chief of the PMU.

The death of the two commanders led to growing calls from Iraqi militia groups and allied political parties to expel U.S. forces from Iraq.

A rocket attack blamed on Kaitib Hizballah in December 2019 killed a U.S. defense contractor and wounded several U.S. and Iraqi soldiers at a military base in the northern Iraqi city of Kirkuk, touching off a cycle of escalation that led to Soleimani's killing and Iran launching retaliatory ballistic missiles at Iraqi bases housing U.S. troops.

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