Four Iraqi federal police officers were killed on Tuesday after a bomb went off southwest of the oil-rich city of Kirkuk, two security sources told Reuters.
The blast took place near the village of Habat, which lies about 40 km (25 miles) southwest of Kirkuk, on the border between Rashad and Daquq districts.
There was no immediate claim of responsibility, but ISIS militants are active in the area. Iraq declared victory over the group, which once held large swathes of the country, in December 2017.
But ISIS has since switched to hit-and-run attacks aimed at undermining the Baghdad government.
Its fighters have regrouped in the Hemrin mountain range in the northeast, which extends from Diyala province, on the border with Iran, crossing northern Salahuddin province and southern Kirkuk.
On Monday, unknown gunmen opened fire on a village 65 km (40 miles) southwest of Kirkuk, killing three residents. There was no immediate claim of responsibility, but police said they believed ISIS was behind the attack.