A loud explosion tore through Kirkuk province after a US-led coalition airstrike took out one of the so-called Islamic State's (IS) largest car-bomb factories on Wednesday, with reports indicating dozens of civilians were killed.

US Central Command confirmed the strike on the facility in the northern Iraq town of Hawija, with the explosion reportedly heard 55 kilometers away in the provincial capital Kirkuk, according to Radio Free Europe. A CENTCOM statement about airstrikes in Iraq and Syria for June 3 specifically references a VBIED, or a vehicle-born improvised explosive device, facility, located in the IS stronghold.

Video from pro-IS media agency al-Amaq, reportedly taken in the aftermath of the explosion, shows injured civilians being carted away on stretchers in the dark into a medical facility. Casualty reports are varied, with Erbil-based Rudaw news stating there were 70 civilian casualties, including 26 children, and another 80 injured. The footage also shows the leveled factory.

Kirkuk province security official Mohammad Khalil al-Juburi confirmed that civilians died during the strike, but he did not provide a specific number. An Iraqi colonel told AFP that the facility contained Humvees, explosives, and tanks.

Meanwhile, in Iraq's western Anbar province, the militant group has reduced the amount of water making its way to pro-government areas. The group has reportedly shut down most of a dam on the Euphrates river located north of the city of Ramadi — which was captured by IS last month — with the water cuts affecting towns downstream.

The reduced water flow will threaten nearby irrigation and water treatment plants, and sources told CNN that the water level was down enough for someone to cross the waterway by foot. The United Nations (UN) said it will look into reports about the alleged activities at the al-Warar dam.

"The use of water as a tool of war is to be condemned in no uncertain terms," the spokesman for the UN secretary-general, Stephane Dujarric, told reporters. "These kinds of reports are disturbing, to say the least."

Dujarric said the UN and its partners will work to "fill in the gaps" and meet water needs for the affected population. In a separate statement on Thursday, the UN's humanitarian coordinator for Iraq, Lisa Grande, said 8 million people impacted by the fighting in Iraq are in need of immediate support, with estimates that the number could rise to 10 million people by the end of the year. She also highlighted the dire straights of the humanitarian mission in Iraq.

"Humanitarian partners have been doing everything they can to help. But more than 50 percent of the operation will be shut down or cut back if money is not received immediately," Grande said.