The United States waged a series of precision air strikes on Thursday against an Iran-backed militia in Iraq that it blamed for a major rocket attack a day earlier that killed two American troops and a 26-year-old British soldier.

 The U.S. strikes appeared limited in scope and narrowly tailored, targeting five weapons storage facilities used by Kataib Hezbollah militants - including facilities used to store weaponry for past attacks on U.S.-led coalition troops, the Pentagon said.

Iraq’s military said in a statement that the U.S. air strikes hit four locations in Iraq. The U.S. military did not estimate how many people in Iraq may have been killed in the strikes, which officials said were carried out by piloted aircraft.

 But there no was no indication of the kind of high-profile killings that President Donald Trump authorized in January, when the United States targeted a top Iranian general, Qassem Soleimani.

U.S. Defense Secretary Mark Esper, in a Pentagon statement detailing the strikes, cautioned that the United States was prepared to respond again, if needed. “We will take any action necessary to protect our forces in Iraq and the region,” Esper said.

 Trump had been quick to authorize the U.S. military to respond following Wednesday’s attack in Iraq, in which militants fired dozens of 107 mm Katyusha rockets from a truck, striking Iraq’s Taji military camp north of Baghdad.

 Out of the roughly 30 rockets fired, some 18 hit the base. No one has claimed responsibility for the attack.