Nineveh Deputy Governor Hassan al-Allaq told Reuters that 113 people had been confirmed dead, with state media putting the death toll at at least 100, with 150 people injured.
The fire ripped through a large events hall in the north-eastern region after fireworks were lit during the celebration, local civil defence said, according to state media.
Iraq’s Interior Ministry said it had issued four arrest warrants for owners of the wedding hall, state media reported, and President Abdul Latif Rashid called for an investigation.
Video from a Reuters correspondent at the site showed firefighters clambering over the charred wreckage of the building, shining lights over smouldering ruins.
Preliminary information indicated that the building was made of highly flammable construction materials, contributing to its rapid collapse, state media said.
Ambulances and medical crews were dispatched to the site by federal Iraqi authorities and Iraq’s semi-autonomous Kurdistan region, according to official statements.
Eyewitnesses at the site said the building caught fire at around 10:45 p.m. local time (1945 GMT) and that hundreds of people were in attendance at the time of the incident.