American soldier on armored vehicle in Iraq
American soldier on armored vehicle in IraqReuters

The US launched air strikes in Iraq on Thursday, American officials said, targeting the Iranian-backed Shiite militia members believed to be responsible for Wednesday’s rocket attack that killed and wounded American and British troops at a base north of Baghdad, The Associated Press reported.

One US official said multiple strikes targeted Kataib Hezbollah weapons facilities inside Iraq. The strikes were a partnered operation with the British, that official said.

The Pentagon later confirmed that the air strikes targeted five weapon storage facilities belonging to Kataib Hezbollah.

The facilities “include facilities that housed weapons used to target US and coalition troops", it added.

The strikes come a day after an American soldier, a British soldier and one US contractor were killed in a rocket attack on the Taji air base north of Baghdad, which hosts troops from the US-led coalition helping local forces battle jihadists.

Hours later, air strikes believed to have been carried out by the US-led coalition targeted Iran-aligned Iraqi fighters in neighboring Syria.

Thursday’s strikes came just hours after top US defense leaders threatened retaliation for the Wednesday rocket attack, making clear that they knew who did it and that the attackers would be held accountable.

Defense Secretary Mark Esper told reporters at the Pentagon earlier Thursday that President Donald Trump had given him the authority to take whatever action he deemed necessary.

"We're going to take this one step at a time, but we've got to hold the perpetrators accountable," Esper said. "You don't get to shoot at our bases and kill and wound Americans and get away with it."

At the White House, Trump had also hinted that a U.S. counterpunch could be coming, telling reporters, "We'll see what the response is." Meanwhile, Army Gen. Mark Milley, chairman of the Joint Chiefs of Staff, told Pentagon reporters the US knows "with a high degree of certainty" who launched the attack.

Tensions have increased in the area since a rocket attack killed a US contractor working at a base in northern Iraq in late December.

Several days later, US F-15 fighter jets bombed five bases used by Kata'ib Hezbollah, a pro-Iranian Shiite group which straddles the boundary between Syria and Iraq, and is allied with the Lebanese terrorist group Hezbollah.

The tensions then continued when a US drone strike outside the Baghdad airport on January 3 killed the head of the Quds Force of the Iranian Revolutionary Guard, Qassem Soleimani, and the Hashed's deputy chief Abu Mahdi al-Muhandis.

Iran then retaliated by launching a volley of ballistic missiles at the western Iraqi base of Ain Al-Asad. While no US personnel were killed in that attack, at least 109 soldiers suffered from brain trauma.