US troops have been training the Iraqi forces in the fight against Daesh, which has lately been losing ground both in Iraq and Syria.
At least two people were killed and six injured when Daesh suicide bombers attacked a base in northern Iraq where US military advisers are stationed, security sources said on Sunday.
In addition, two suicide bombers died when they detonated their vests at the entrance to the K1 base overnight, and three more were killed by Kurdish peshmerga forces. The peshmerga control the Kirkuk area where the base is situated.
"They were wearing uniforms like the Kurdish peshmerga and had shaved their beards to look like us," one officer told Reuters.
Daesh claimed responsibility for the attack in a statement.
Iraqi forces backed by a US-led coalition are fighting to dislodge Daesh from Mosul, 140 km north-west of Kirkuk, but large pockets of territory remain under militant control, including Hawija, which is near the targeted base.
Driving out Turkmen
The attack comes as Human Rights Watch said that the Kurdistan Regional Government were forcing Sunni Turkmen to leave the city.
According to the report, Turkmen who were internally displaced said that their identity and benefits cards were confiscated.
They added that they experienced threats and harassment for the purpose of pushing them to Shia-majority areas controlled by the Popular Mobilization Forces, a pro-government militia.
"KRG forces should cease harassing Turkmen and unlawfully forcing them to leave Kirkuk," Human Rights Watch's deputy Middle East director Lama Fakih said.