The US carried out airstrikes in Iraq and Syria targeting an Iran-backed Iraqi militia blamed for a rocket attack that killed an American defense contractor and wounded four US service members, the Pentagon said Sunday.

The US retaliation threatens to unleash a dangerous spiral of escalation and backlash against the US military presence in Iraq at a time the country is politically unstable following nearly three months of deadly anti-government protests.

US forces "conducted precision defensive strikes" against three Kataeb Hezbollah bases in Iraq and two others in Syria, Defense Department spokesman Jonathan Hoffman said in a statement.

The strikes will "degrade KH's ability to conduct future attacks," he said, using an acronym for the group, adding that weapons facilities and command and control centers used to plan attacks against US forces were hit.

At least 19 fighters were killed, Iraqi militia sources said.

Retaliation

The US blamed Kataeb Hezbollah for a rocket barrage on Friday that killed an American defense contractor and wounded four US soldiers at the K1 Iraqi military base in Kirkuk in the north of the country. Several Iraqi soldiers were also wounded.

Kataeb Hezbollah is backed by the Iranian Revolutionary Guard's elite al-Quds force. Led by one of Iraq's most powerful men, Abu Mahdi al-Muhandis, the militia is part of the Popular Mobilization Units mobilized to fight against the "Islamic State" group.

He once fought US troops during the post-Saddam Hussein military occupation and is now the deputy head of the Popular Mobilization Forces.

Hours after the US strikes, four rockets exploded near a base housing US troops close to the capital Baghdad without wounding anyone, an Iraqi security official told AFP.

In response to the attacks, Kataib Hezbollah called for the expelling of the "American enemy" from Iraq.

"The military, security forces as well as popular and patriotic powers have to expel the American enemy," it said.

Another powerful pro-Iran militia, Assaib Ahl al-Haq — which was recently slapped with US sanctions — similarly called for US forces to withdraw from Iraq.

"The American military presence has become a burden for the Iraqi state and a source of threat against our forces," it said in a statement. "It is therefore imperative for all of us to do everything to expel them by all legitimate means."

Instability

The rocket attack on the base in Kirkuk and US relation come at a time the country is engulfed in nearly three of anti-government protests that have killed more than 450 people and injured 25,000. The protests against corruption, poor services and a dire economy have been directed at the entire political class and increasingly against Iranian meddling in the country.

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The protests and a call by Iraqi's top Shiite cleric for a change of government government forced Prime Minister Adel Abdul-Mahdi to resign late last month. He remains caretaker prime minister.

Abdul-Mahdi said nothing following Friday's attack in Kirkuk, but on Sunday criticized the United States.

He called the US strikes a violation of Iraqi sovereignty and a "dangerous escalation that threatens the security of Iraq and the region,'' according to a statement issued from his office.

Abdul-Mahdi said US Defense Secretary Mark Esper notified him shortly before the airstrikes and ignored a request to call off US retaliation plans.

The statement also said a US diplomat contacted President Barham Salih, who had also requested the US not carry out the attack.

US forces targeted

Since late October, at least 11 attacks have targeted Iraqi military bases where US soldiers or diplomats are deployed. The US has blamed Iran-backed militia and warned of retaliation.

The escalation comes after pro-Iranian militia in Iraq blamed Israel for a series of strikes on weapons facilities in July and August, leading to calls in Iraq for US forces to exit the country.

Earlier this week, Israeli Army Chief of Staff Lt. Gen. Aviv Kochavi said Iran is increasingly moving advanced weaponry into Iraq and hinted that Israeli forces were countering Tehran in Iraq.

The Israeli military is taking action "in the open and undercover, not to allow the enemy to equip itself with high-accuracy weapons, even at the price of confrontation," he said.

Israel has carried out scores of attacks on Syrian government forces, Iranian forces and allied militia in Syria during the course that country's civil war.

cw/se (dpa, Reuters, AP, AFP)

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