Five Iraqi troops were killed Thursday when their helicopter crashed on a "combat mission" north of Baghdad, the military said, as a security source confirmed it had been hit by ground fire.

The helicopter came down near Amerli in Salaheddin province, the military said, in an area where Iraqi troops have carried out repeated operations against suspected sleeper cells of the Daesh terrorist group.

Video footage sent to journalists in Baghdad showed firefighters attempting to put out a blaze in the wreckage of the aircraft.

The security forces had launched an operation on Tuesday to "search and clear areas in the south of Kirkuk province," which borders Salaheddin, a statement on their Twitter account said.

The security source told Agence France-Presse (AFP) that the helicopter that came down was one of two that had been checking pylons carrying high-voltage power lines in the area, a frequent target for holdout militants in recent months.

As the two aircraft approached Amerli district, one of them took a "direct hit" which forced it down.

Daesh lost its last territory in Iraq in 2017 after a bloody three-year campaign that put paid to its hopes of forging a transnational "caliphate" straddling the border with Syria.

But the terrorists retain sleeper cells in desert and mountain areas that they have used as launchpads for attacks in Iraq's cities.

A July 19 suicide bombing claimed by the Daesh terrorist group killed 30 people in a street market in a Shiite district of Baghdad.