Fighters downed the Mi-35 helicopter between the towns of Beiji and al-Senniyah in northern Iraq, an official with the Iraqi Defense Ministry said. An official with the Iraqi air force corroborated the information, saying the helicopter's pilot and co-pilot were killed in the crash.
Beiji, located 200 kilometres north of Baghdad, is home to Iraq's biggest oil refinery.
Both officials spoke on condition of anonymity as they are not authorised to speak with journalists.
The shoot down of the helicopter shows the Islamic State group's ability to counter air operations, potentially putting at risk US led airstrikes in the country. US Central Command said it had carried out airstrikes in Sinjar and Fallujah over Thursday and Friday.
Iraq's most revered Shiite cleric called on al-Abadi to create a national security force that doesn't promote sectarianism at a time of heightened tensions between ethnic and religious groups.
The national guard, proposed by al-Abadi, should be a force of "patriotism and purity" to help pull the country out of the crisis, the reclusive al-Sistani said in his Friday sermon delivered by his spokesman Abdul Mehdi Karbalaie in the city of Karbala.
An Iraqi Cabinet also was selected on Sept. 8, with the exception of the key posts of the defense and interior ministers, with lawmakers failing to agree on who should be nominated. Al-Sistani called upon al-Abadi to select candidates for these critical roles following the Islamic Eid al-Adha holiday next week.
