Almost 150 people, including 80 women and children, were on board the boat that was destined for a popular tourist island in Mosul as part of the Kurdish New Year celebrations, AP News reports. So far, 12 people have been rescued, Khalil added. Some were seen jumping in to try to help.
Mosul was devastated by the war against the Islamic State group, which occupied the city for three years.
The river's level was high because of a rainy season that brought more precipitation than previous years.
Khalil said the vessel sank because of a technical problem, and there were few boats in the area to rescue people. The overcrowded ferry exceeded the permitted capacity by two times and most of the passengers on board could not swim, reported BBC.
The small boat, which was carrying people to a popular picnic area, was believed to be carrying around 150 people when it overturned.
"I can not describe the scene, it's a catastrophe", he said.
Five ferry workers were arrested late on Thursday, security sources said.
Iraqi Prime Minister Adel Abdul-Mahdi ordered an investigation and, according to Iraqi TV, arrived in Mosul later Thursday.
Nowruz, or the Persian new year, dates back to 1700 BC and incorporates Zoroastrian traditions.
Rescue efforts are underway after the ferry capsized on the Tigris river in the Iraqi city of Mosul.
It is the most important event in the Iranian calendar and is widely celebrated across the territories of the old Persian empire, from the Mideast to Central Asia.