A Pentagon official downplayed the incident, saying he "assumed" ISIS fighters got no closer than a couple of hundred meters before they "ran away in fear."He also insisted that there were no casualties during this attack.

The previous attack, on Saturday, saw ISIS rockets hitting the base, killing a US Marine and wounding several others. Despite initial Pentagon claims that the number of wounded was "less than five," they are now reporting at least eight wounded in the incident.

The size of the base and the number of US troops positioned there are both unclear. As a response to Saturday's attack, the Pentagon has  announced an additional deployment of Marines to participate in combat operations in Iraq.