Iraq declared IS defeated in late 2017 but remnants of the group still wage hit-and-run attacks on security forces in remote areas of the north and west.

Early Saturday, the jihadists attacked fighters of Iraq's Hashed al-Shaabi paramilitary force stationed outside a town about 180 kilometres (110 miles) north of Baghdad, according to a statement by Iraq's security forces.

"Six fighters were killed. As another unit was dispatched to reinforce them, an explosive device detonated on that convoy and killed three fighters," the statement said.

A 10th fighter was killed in a separate IS attack on nearby unit from the Hashed, a network of armed groups incorporated into the regular army chain of command.

A security source in Salahaddin province, where the attack took place, told AFP that the first IS ambush took place just before midnight.

"All the Iraqi security forces manning the checkpoint were killed. F16 planes are flying overhead to search for the IS fighters," the source said.

The attack was IS's deadliest in several months and appeared to cap a period of more numerous and aggressive operations.

Last week, the jihadists claimed a suicide attack that wounded four outside an intelligence headquarters in the northern province of Kirkuk.

"The group's attacks have seemingly grown bolder over the past month or so, as it's increasingly launched direct assaults on Iraqi security forces and carried out some daytime attacks," Sam Heller, an independent analyst focused on IS and Iraq, told AFP.

"Last night's attack, if it was in fact coordinated between several IS units, would mark a new escalation by the group," he added.

IS overran around a third of Iraq in 2014, triggering the creation of both a US-led coalition to defeat the jihadists and the Hashed, comprised mostly of Shiite units with ties to Iran -- Iraq's neighbour but a foe to Washington.

The two forces are at odds in Iraq, as the US blames hardline Hashed factions for deadly rocket attacks on its troops while the Hashed and allied politicians have demanded US troops leave the country.

In recent months, the coalition has pulled back from five bases where it had been deployed to help track down IS sleeper cells, saying the Iraqi military could largely finish the fight on their own.

The coalition is still backing Iraqi troops with air strikes, intelligence and surveillance.