Kurdish authorities in Iraq have accused Iran of sending 30,000 soldiers and military experts to fight the Islamic State of Iraq and the Levant (ISIL) group.
Shakhawan Abdullah, the head of the Iraq's parliamentary security and defence committee, told Al Jazeera on Sunday that Iranian soldiers were operating in a number of Iraqi cities and fighting on Iraqi soil.
Abdullah said Iran's presence went beyond military advisers and experts, and that Iranians were fighting under the banner of the Popular Mobilisation Forces.
The Popular Mobilisation Forces is an umbrella organisation of Shia armed groups composed of around 100,000 fighters.
Iran has repeatedly denied sending soldiers to Iraq despite claims by the US.
In August, Iran was accused of sending hundreds of soldiers to retake the town of Jalawla from ISIL, while in December it was alleged that an Iranian F-4 fighter struck ISIL targets in the province of Diyala.
Shia fighters have been accused of killing dozens of civilians in retribution against the actions of ISIL since the group seized large swathes of land and announced the establishment of a "caliphate" straddling the two countries.