(CNN) The three coalition members wounded when rockets struck a military base in Iraq on Saturday were US personnel, a US military official told CNN.

It was not immediately clear whether they were military personnel or civilian.

The al-Taji base was hit by its second rocket attack in a week early on Saturday local time, Col. Myles B. Caggins III, a spokesman for the international Operation Inherent Resolve (OIR), confirmed on Twitter.

Caggins said three coalition troops and two Iraqi troops were wounded and authorities were assessing the damage.

Iraq's Baghdad Operations Command said earlier on Saturday that several Katyusha rockets landed inside the airbase.

In a statement, the Operations Command said they knew where the rockets were fired from.

"Our security forces have discovered the location of the firing of Katyusha rockets that targeted al-Taji airbase north of the capital Baghdad this morning. We discovered 7 rocket launchpads inside a parking garage in the area of Abu al-Ezzam," it said.

The statement added that the owner of the parking garage, employees and all those present were taken in for questioning by Baghdad police.

These photos from the international Operation Inherent Resolve show the impact of the strike on Saturday.

The Joint Operations Command described the attack as "brutal" and said the injured Iraqis were "all in a critical condition."

There have been multiple rocket attacks in Iraq in recent weeks. Two US service members and one British coalition service member were killed and around a dozen others injured in an attack on the same base on Wednesday.

The US said Thursday it had assessed that an Iranian-backed group was responsible for the rocket attack.

The two Americans were the first to die in a rocket attack in Iraq since December when a US contractor was killed in another attack on a base near Kirkuk.

The December attack prompted retaliatory US airstrikes against militia targets in Iraq and Syria. Trump administration officials pointed to the contractor's death as their justification for air strikes that killed Iran's second most powerful leader, Gen. Qassem Soleimani, and spiked tensions around the world.

The latest attack on the al-Taji base comes after the US carried out retaliatory airstrikes on Thursday against multiple Iranian-backed militia sites in Iraq, according to the US Defense Department.

At least six people were killed -- five of them military personnel -- and 11 others were injured by the US-led coalition air strikes, Iraqi military said in statement.

The Iraqi military said the US-led coalition attack violated the partnership agreement.

"The joint operations command strongly condemns this attack that targeted the Iraqi military establishment, which violates the principle of partnership and coalition between the Iraqi security forces and the party that planned and executed this treacherous attack."

Correction: This story has been updated to reflect that the two American deaths were the first from a rocket attack in Iraq since December.