Islamic State group fighters battling Iraqi forces in Mosul are holding civilians hostage in buildings and then deliberately attracting strikes by coalition aircraft, a spokesman for the US-led coalition said on Thursday.

His comments come after the senior US leader in Iraq, General Stephen Townsend, acknowledged this week that a coalition strike in the northern city earlier this month "probably" killed dozens of civilians.

"What you see now is not the use civilians as human shields," said Colonel Joe Scrocca, a spokesman for the Baghdad-based coalition. "Now it's something much more sinister."

"ISIS is smuggling civilians so we won't see them and trying to bait the coalition to attack to take advantage of the public outcry and the terror," he added, using an alternate acronym for the IS group.

"For the first time we caught that on a video yesterday," he said. "Armed ISIS fighters forced civilians into a building, killing one who resisted, and then used this building against the CTS (Iraqi counter-terrorist forces)."

US military leaders say the ammunition used in the coalition strike on civilians this month was insufficient to explain the amount of destruction and number of casualties observed.

They suspect the building may have been booby-trapped or that the damaged may have been caused by the detonation of a truck bomb.

The coalition is supporting Iraqi forces battling the jihadists in Mosul, whose numbers are estimated to have fallen to fewer than 1,000, Scrocca said.

The IS group had an estimated 2,000 fighters in west Mosul when the Iraqi push on the northern city began in mid-February. "We believe it's less than half now," he said.

The Iraqi forces number around 100,000 men, he added.

Having pushed the jihadists from the city's eastern section, they are now moving into the old city in western Mosul, where tens of thousands of civilians are believed to be trapped.

Source: AFP