The six were gunned down in the Taza Khurmatu district south of the city of Kirkuk, said Hussein Adel, the local adminstration head, adding that a seventh person, a civilian, was also missing.

After the killings, a police car arriving in the area came under fire, and a bomb was also exploded.

"IS set fire to farmland," Adel said. "When police and civilians came to put out the fire, they were attacked by IS elements, who killed three policemen and three teenagers."

Iraq announced victory against IS in late 2017 after three years of ferocious fighting backed by paramilitary forces and the US-led air coalition.

But IS cells still carry out hit-and-run attacks, particularly in vast desert regions of northern and western Iraq near the porous border with Syria.

In recent years, they have torched swathes of fields in Iraq and Syria, boasting about the destruction in their propaganda.

In 2019, more than 200 fires burned down some 5,000 hectares (12,355 acres) of crops in northern Iraq, with some of the blazes blamed on jihadists, and others on land disputes.

After three years of biting drought that has slashed cultivatable areas by half, Iraq is closely monitoring its wheat harvest this year.

The IS group has " maintained the ability to launch attacks at a steady rate in Iraq, including hit-and-run operations, ambushes and roadside bombs", a UN report said in January.

"Exploiting the porous border" between Iraq and Syria, the jihadist group still has "between 6,000 and 10,000 fighters across both countries, where it is forming cells and training operatives to launch attacks".

Cells "remain active in desert and rural territories, and the group uses urban areas to expand its clandestine networks", it added.

In April, two soldiers were killed by a suicide bomber during a counter-terrorism operation in an area north of the capital Baghdad.