The Islamic State has started using more sinister tactics in the five-month long fight for Mosul, a sign the terror group is getting even more desperate as its numbers dwindle, a spokesman for the U.S.-led coalition said on Thursday.

“ISIS is smuggling civilians into buildings so we won’t see them, and trying to bait the coalition to attack,” said Col. Joseph Scrocca, who said the new tactic was caught on video for the first time on Wednesday.

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Scrocca said the video would be released to the public as soon as it is declassified.

ISIS was using the tactic in an effort to take advantage of the “negative impact” civilian casualties have on the U.S.-led coalition’s efforts.

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As a result of the barbaric tactics, Scrocca said the U.S. military would adjust its own tactics going forward.

“We know what to look for,” Scrocca said. “It has caused some adjustments to our procedures.”

He added: “We have always tried to have a munition that is proportional to the target. We don’t need to use a 500-pound bomb which is going to destroy a building if we can use a Hellfire [missile], which is just going to blow out a room and kill some fighters."

Echoing Wednesday congressional testimony from Gen. Joseph Votel, the head of U.S. Central Command, Scrocca also said, “Our goal is and has always been zero civilian casualties.”

The top U.S. commander in Baghdad, Lt. Gen. Stephen Townsend, has ordered a formal investigation into the Mosul strike on March 17 which is set to include strikes days before and after the coalition bombing that likely killed upwards of 100 civilians.

Air Force Brig. Gen. Matthew Isler will lead the investigation.

Asked if the U.S. military was alarmed at the high number of casualties suffered by the Iraqi military in Mosul -- 774 killed and 4,600 wounded, according to Votel -- Scrocca declined to weigh in.

On March 1, Lt. Gen. Stephen Townsend estimated ISIS had 2,000 fighters in Western Mosul.

“We believe it’s less than half of that now,” Scrocca said.