Nine Iraqi police officers killed in suspected IS attack in Kirkuk
No group immediately claimed responsibility for the attack, one of the deadliest in Iraq in recent months.
The bomb blast in the Kirkuk area hit a vehicle transporting members of Iraq's federal police.
It was followed by "a direct attack with small arms" near the village of Shalal al-Matar, a federal police officer told AFP on condition of anonymity, attributing the assault to IS.
"An assailant has been killed and we are looking for the others," the officer said.
Two policemen initially reported as being wounded later died, bringing the total killed to nine.
IS jihadists seized large swathes of Iraqi and Syrian territory in 2014, declaring a "caliphate" where they ruled with brutality before their defeat in late 2017 by Iraqi forces backed by a US-led military coalition.
IS lost its last Syrian bastion, near the Iraqi border, in 2019.
Iraqi Prime Minister Mohammed Shia al-Sudani condemned the violence as a "cowardly terrorist attack".
Security forces should show "vigilance, carefully inspect the roads and not provide any opportunity for terrorist elements", he said.
The US-led anti-IS coalition continued a combat role in Iraq until December last year, but roughly 2,500 American soldiers remain in the country to assist in the fight against the jihadists.
IS cells, however, remain active in several areas of Iraq.
On Wednesday, three Iraqi soldiers were killed and three others injured when a bomb exploded as their patrol vehicle passed through farmland in Tarmiya, a rural municipality located about 30 kilometres (20 miles) north of the capital Baghdad.
There was no immediate claim for the bombing in a known hotspot of IS sleeper cells.
Last month a machine gun attack on a remote northern Iraqi military post killed four soldiers near Kirkuk, a military source said. There was no immediate claim of responsibility.
Iraqi security forces continue to carry out counter-terrorism operations against the group, and the deaths of IS fighters in airstrikes and raids are regularly announced.
Despite the setbacks, which has left IS a shadow of its former self, the group has "maintained its ability to launch attacks at a steady pace", a January report by the United Nations read.
The UN estimates the jihadist organisation maintains between 6,000 and 10,000 fighters inside Iraq and Syria, exploiting the porous border between the two countries and concentrating mainly in rural areas.