Taji military base attack truck
Washington CNN  — 

Iranian-backed militias were responsible for the rocket attack that killed two US troops and a UK service member in Iraq Wednesday and the US is reviewing options as to how to respond, the US Defense Secretary and top US general said Thursday.

“Yesterday’s attack by Iranian backed Shia militia groups consisted of multiple indirect fires that originated from a stationary platform and was clearly targeting coalition and partner forces on Camp Taji,” Secretary of Defense Mark Esper told reporters at the Pentagon while pledging that the US would take action to hold the attackers accountable.

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

President Donald Trump told reporters Thursday that he had been working on the attack issue Wednesday night.

“They’ve sent a lot of rockets now. It hasn’t been fully determined it was Iran,” Trump said, adding “It was a rebel group, but most likely it looks like it could be backed by Iran.”

The Chairman of the Joint Chiefs of Staff, Gen. Mark Milley, said Thursday that the truck that fired the approximately 30 107mm rockets was captured by the Iraqi Security Forces and that forensics from that vehicle helped identify who the attackers were.

“We have pretty good confidence who did this. We were able to capture the truck, it was a modified truck with tubes, rocket tubes on the back, the Iraqi security forces did a good job in helping secure that truck. We have good indications based on forensics where it was fired from, who did the firing and so on and so forth,” Milley said.

Milley said that 14 coalition personnel were also wounded in the attack, including five injuries that were considered “urgent.” Those wounded included US, UK, Polish and contractor personnel.

“The groups responsible will be held accountable appropriately,” Milley said, adding “it was a significant attack and it resulted in the death and wounding of American soldiers, airman,sailors, Marines sort of thing. So where we go from here as you would expect options are on the table and we are looking at everything and we will await final options and decisions from the President.”

Trump declined to say Thursday what the US response will consist of when asked at an appearance at the White House.

Asked if a retaliatory strike could include US airstrikes against targets in Iran, Esper said “I’m not going to take any option off the table right now but we are focused on the group, groups, that we believed perpetrated this in Iraq.”

Earlier on Thursday the commander of US Central Command, which oversees US military forces in the region, Gen. Kenneth McKenzie said that “the Iranian proxy group Khatib Hezbollah is the only group known to have previously conducted an indirect fire attack of this scale against US and Coalition forces in Iraq.”

There have been multiple rocket attacks in Iraq in recent weeks, but Wednesday’s fusillade was the first to cause a US death since December, when a US contractor was killed. That death prompted retaliatory US airstrikes against Iranian-backed 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.

CNN’s Barbara Starr, Michael Conte and Nicole Gaouette contributed to this report.