AN Iraqi military unit containing Australian and US military advisors have been caught up in a chemical gas attack reportedly carried out by Islamic State.

CBS News reports that 25 Iraqis required treatment but that none of the advisers were injured by the mustard gas.

Brigadier General Yahya Rasool told the AP that six soldiers were treated for breathing problems.

The ABC says the Pentagon has described the attack as largely ineffective.

A US Defense official has told the ABC the foreign advisers were medically screened and showed no signs of exposure and have returned to duty.

The attack occurred a day after an Iraqi military officer said ISIS militants had launched a gas attack in the al-Abar neighbourhood in western Mosul.

Two army officers say masks and other equipment have been distributed to forces in case of future gas attacks. They spoke anonymously because they were not authorised to speak to media.

Australian Prime Minister Malcolm Turnbull was briefed on the attack this morning.

Mr Turnbull said he had received word that no Australian troops were affected by the chemical attack but had assisted after it occured.