U.S. air strikes against Daesh targets between September and February resulted in the deaths of 20 civilians and injured 11 others, the Pentagon said Friday.

The acknowledgement brings the official tally of civilians killed in US-led strikes in Iraq and Syria to 41 since counter-Daesh operations began in August 2014. In addition, a total of 28 civilians have been injured, the Pentagon claims.

"In this type of armed conflict, particularly with an enemy who hides among the civilian population, there are going to be, unfortunately, civilian casualties at times," U.S. Central Command (CENTCOM) spokesman Colonel Pat Ryder said.

"We do everything we can to avoid it, but that's just the nature of the enemy we are dealing with."

Observers say the number of civilian casualties killed in the 12,000 or so plane and drone strikes is likely far higher.

One of the incidents disclosed Friday occurred October 5 in Atshanah, Iraq when a strike on Daesh fighters at a mortar position also killed eight civilians.

A January 11 attack on a cash distribution system near the Iraqi city of Mosul killed one civilian and injured five others.

That particular strike drew international attention because military video of the attack showed millions of dollars worth of cash fluttering across the city afterward.

"The coalition takes all feasible precautions to avoid civilian casualties during the course of military operations," CENTCOM said in a statement.

"In all of the cases released today, assessments determined that although the strikes complied with the law of armed conflict and all appropriate precautions were taken, civilian casualties unfortunately did occur."

The strikes took place between September 10 and February 2.