The victims were "killed in an ambush by the jihadists" overnight Sunday to Monday, the security source said on condition of anonymity.

Meanwhile, the same night six shepherds in the neighbouring province of Saladin were kidnapped by IS, a different security source said.

The level of violence has considerably decreased since Iraq declared victory over the Islamic State group in December, following three years of battling the jihadists.

IS seized nearly a third of the country's territory after a lighting offensive launched in 2014.

The jihadists continue to perpetrate isolated attacks and experts warn of the presence of areas which are difficult for Iraqi forces to control.

They include the mountainous zone within Kirkuk region, north of Baghdad, and the desert which borders war-torn Syria.