The crash appeared to have been accidental, as there were no indications it was caused by hostile fire, Pentagon spokesman Colonel Rob Manning said.

A statement from the US-led coalition that is helping Iraqi partners fight the Islamic State group said the crash occurred around 2200 GMT on Sunday.

"All personnel were recovered by coalition forces immediately following the incident and three were evacuated for further treatment," Manning said.

Manning did not release the nationalities of the injured.

Officials did not provide immediate details on the location of the crash but noted it was "conducting a partnered counterterrorism mission."

The United States leads an international coalition that has targeted IS and other jihadists in Iraq and neighboring Syria since 2014.

The coalition includes Britain, France, Saudi Arabia and Turkey along with Australia, Bahrain, Canada, Jordan, the Netherlands and the United Arab Emirates.

In March seven US troops were killed when their helicopter crashed during a transport mission in western Iraq, near the border with Syria.

Later that month two coalition members -- an American and a Briton -- were killed by an improvised explosive device in the northern Syrian city of Manbij.