U.S. airstrikes killed eight civilians over a three-month period last year, according to statement released Friday by U.S. Central Command.

Five airstrikes in Iraq and Syria between April 12 and July 4 "likely resulted in the death" of eight civilians and three others wounded, the release said. Two of the strikes were in Iraq and the other three were in Syria.

In at least two of the cases, officials determined that civilians entered the target area after the U.S. aircraft had already released their weapons.

Some have been critical of the administration's restrictive rules of engagement, saying that they are too strict and prevent troops from striking the enemy when they have a chance.

"We can step up the air campaign by easing overly-restrictive rules of engagement," Sen. John McCain, R-Ariz., said in a speech on the Senate floor following the attacks in Paris in November.

But the Pentagon has defended the restrictive rules of engagement as necessary to keep civilian casualties as low as possible.

"We deeply regret the unintentional loss of life and injuries resulting from those airstrikes and express our deepest sympathies to the victims' families and those affected," the Central Command statement said.