US Central Command is investigating an air strike by coalition forces in Mosul that may be responsible for dozens of civilian deaths.

CENTCOM says that a strike on ISIS fighters and equipment did occur in the area where up to 200 civilians were killed, but they are unable to confirm whether the deaths were due to the air strike.

The strike was called in by Iraqi forces who are battling to retake the city from ISIS.

NBCNews:

Officials had previously confirmed an investigation was underway as to whether the strike was executed by the U.S. rather than by other coalition members, or even by ISIS.

It comes as Iraqi vice president Osama al-Nujaifi, who is from Mosul, described the incident as a "humanitarian catastrophe" blaming the U.S.-led coalition airstrikes and the excessive use of force by federal police forces.

He called for an emergency session of the Iraqi parliament to discuss the catastrophe and to begin a parliamentary investigation into its cause.

The strike comes in the same month as two other high-profile strikes in Syria, where the coalition is also fighting ISIS. In total, the three strikes have resulted in unconfirmed reports of upwards of 350 civilian casualties.

The vice president said a change in the rules of engagement — which are meant to minimize civilian casualties in Iraq and Syria — had resulted in the "martyrdom of hundreds of civilians".

A senior U.S. defense official denied on Saturday that there had been any change in the rules of engagement. The CENTCOM statement said "our goal has always been for zero civilian casualties."

A civilian casualty report is issued monthly, CENTCOM added, verifying allegations and that coalition airstrikes are executed in compliance with the Law of Armed Conflict.

March could prove to be the deadliest month for civilians at the hands of U.S. airstrikes since the war began, potentially taking the tally to more than 1,000 civilians killed.

The New York Times quotes an Iraqi military source in explaining how so many civilians were killed:

Iraqi officers, though, say they know exactly what happened: Maj. Gen. Maan al-Saadi, a commander of the Iraqi special forces, said that the civilian deaths were a result of a coalition airstrike that his men had called in, to take out snipers on the roofs of three houses in a neighborhood called Mosul Jidideh. General Saadi said the special forces were unaware that the houses’ basements were filled with civilians.

“After the bombing we were surprised by the civilian victims,” the general said, “and I think it was a trap by ISIS to stop the bombing operations and turn public opinion against us.”

The Iraqi military has halted all offensive operations while the investigation proceeds. 

What seems clear is that ISIS, as it always has done, is hiding behind civilians hoping to deter attacks on their positions, or failing that, reaping a propaganda victory when civilians die. CENTCOM denies that the rules of engagement have changed and the fact that the coalition aircraft were unaware that civilians were hiding in the basements of those houses confirms that.

The death of civilians in wartime is a tragedy. But the enemy has made their deaths a part of their war effort. That has been their choice. We either continue to execute operations with care toward civilians as we have been doing, or basically surrender the initiative to the enemy. The latter choice is unacceptable, which means we haven't seen the last of accidental civilian deaths.