BAGHDAD - Iraqi government air strikes against jihadists, some with the use of barrel bombs, have killed at least 75 civilians since the start of June, Human Rights Watch said Wednesday.

The New York-based rights group said hundreds of civilians had also been wounded in such strikes since June 6.

"The government's air strikes are wreaking an awful toll on ordinary residents," HRW's deputy Middle East director Joe Stork said in a statement.

The watchdog documented 75 civilian deaths in four cities since last month's launch of a sweeping military offensive by the jihadist Islamic State (IS) and allied Sunni armed groups.

At least 17 of the deaths had resulted from the use of barrel bombs.

The crude devices, which the Syrian regime has also used against rebels over the past two years, are barrels stuffed with fertiliser, shrapnel or any improvised explosive mix.

They are much cheaper than conventional weapons but less accurate.

"Despite repeated government denials, government forces have resumed the use of the deadly barrel bombs in populated areas of Fallujah," HRW said.

"Governments that are helping Iraq in its military campaign should pull back their aid until Iraqi forces and any other groups supporting them end their indiscriminate attacks on civilians," Stork said.

Iraq has received military assistance in various forms from the United States and Iran in its battle against IS advances north of the capital that at one point looked like threatening Baghdad.

The HRW report also said that hospitals in the cities of rebel-held Fallujah and Baiji had repeatedly come under attack by Iraq's air force.