• Video report by ITV News Security Editor Rohit Kachroo

An Iranian-backed militia has vowed to exact revenge for the “aggression of evil American ravens”.

The announcement in Baghdad came a day after US defence secretary Mark Esper said Washington had carried out military strikes targeting the Iranian-backed Iraqi militia blamed for a rocket attack that killed an American contractor in Iraq last week.

Secretary of state Mike Pompeo said the strikes send the message that the US will not tolerate actions by Iran that jeopardise American lives.

The US military said “precision defensive strikes” were conducted against five sites of Kataeb Hezbollah, or Hezbollah Brigades in Iraq and Syria.

“Our battle with America and its mercenaries is now open to all possibilities,” Kataeb Hezbollah said in a statement. “We have no alternative today other than confrontation and there is nothing that will prevent us from responding to this crime.”

The US blames the militia for a rocket barrage that killed a US defence contractor at a military compound near Kirkuk, in northern Iraq. Officials said as many as 30 rockets were fired in that attack.

Iraq’s Hezbollah Brigades, a separate force from the Lebanese militant group Hezbollah, operates under the umbrella of the state-sanctioned militias known collectively as the Popular Mobilisation Forces. Many of them are supported by Iran.

Paramilitary Popular Mobilisation Forces Credit: AP/Nasser Nasser

The Popular Mobilisation Forces said the US strikes killed at least 19 of Kataeb Hezbollah’s members. But Kataeb Hezbollah spokesman Mohammed Mohieh told The Associated Press that the death toll rose to 25. At least 51 militiamen were wounded and some of them were in serious condition, he said, adding that the militia group’s commanders would decide on the retaliation.

In Tehran, foreign ministry spokesman Abbas Mousavi condemned the US strikes against Kataeb Hezbollah as an “obvious case of terrorism” and accused Washington of ignoring Iraq’s sovereignty.

Lebanon’s Iran-backed Hezbollah also blasted the “brutal American aggression” saying those who took the decision to carry out the attack “will soon discover how stupid this criminal decision was”.

Kataeb Hezbollah is led by Abu Mahdi al-Muhandis, one of Iraq’s most powerful men. He once battled US troops and is now the deputy head of the Popular Mobilisation Forces. In 2009, the State Department linked him to the elite Quds Force of Iran’s Revolutionary Guard, designated a foreign terrorist organisation by US President Donald Trump earlier this year.

The US maintains some 5,000 troops in Iraq, at the invitation of the Iraqi government to assist and train in the fight against the Islamic State group.