Fighters from the Islamic State group shot down an Iraqi military helicopter Saturday, killing two pilots on board, The Associated Press (AP) reported. The attack raises concerns about the safety of aircrafts that are conducting U.S.-led airstrikes against the group in Iraq and Syria.

The attack happened in the Shiite holy city of Samarra, about 60 miles north of Baghdad. A senior defense official told AP that a shoulder-fired rocket launcher was used by the militants to attack an EC635 chopper. The chopper, manufactured by Airbus Helicopters, is used for transportation, surveillance and combat, AP reported.

Local officials suspect that the group, which has been demanding an Islamic Caliphate in the region and has taken control over a third of Iraq and Syria, may have obtained such weapons while raiding army bases in these countries.

Earlier in October, two other Iraqi military helicopters were shot down by ISIS militants near the oil refinery town of Beiji, 130 miles north of Baghdad. Soon after, the group also released a guide on social media, explaining how to shoot down a plane.