Two Americans and one Brit were killed as more than 15 Katyusha rockets hit an Iraqi base housing U.S. troops Wednesday, the U.S. military said in a statement.

"The Coalition @CJTFOIR confirms more than 15 small rockets impacted Iraq’s Camp Taji base hosting Coalition troops, March 11 at 7:35 p.m. (Iraq Time)," Operation Inherent Resolve (OIR) spokesperson Col. Myles Caggins said on Twitter.

Caggins added that an assessment and investigation are ongoing.

The attack comes just days after two U.S. service members were killed by enemy forces while advising and accompanying Iraqi Security Forces during a mission to eliminate an ISIS terrorist stronghold in a mountainous area of north-central Iraq on Sunday.

The U.S. military could not confirm who is responsible for Wednesday's attack but one source told Fox News that "ISIS doesn't have this capability." Read more a FOX News