At least 11 people have been killed in Iraq after attackers hit a police checkpoint and then detonated a car bomb at the entrance to the city of Tikrit.

Iraqi police and military officials said on Saturday that there was no immediate claim of responsibility for the attack on the city, which is 150km north of Baghdad.

Tikrit was retaken from Islamic State of Iraq and the Levant - ISIL also known as ISIS - in April 2015.

The attack came days after Iraqi forces recaptured the town of Shirqat, 100km north of Tikrit, from ISIL in preparation for a move on the northern city of Mosul later this year. 

Iraq: Security forces recapture Shirqat from ISIL

One of Saturday's attackers was killed at the checkpoint after shooting dead four police officers at around 5am local time (0200 GMT), according to police and sources from Salahuddin Operations Command, which is responsible for security in the area.

Two other assailants managed to drive about 7km to the city limits before detonating the explosives in their pick-up truck, killing eight people and wounding 23, sources told Reuters news agency.

A provincial spokesman told the AP news agency the attack was a triple suicide bombing.

Colonel Mohammed al-Jabouri said three assailants rammed their explosives-laden vehicles into the checkpoint. 

Al-Jabouri said 12 security officers were killed and 34 others were wounded.

He said the attack occurred as the local police chief and head of the provincial security committee were visiting the site. Both escaped unharmed.

The governor of Salahuddin province, Ahmed al-Jabouri, accused ISIL of being behind the attacks, vowing to "retaliate for the martyrs by chopping off the heads of Daesh" fighters, using the Arabic acronym for the group.

No group has claimed responsibility for the attacks, but ISIL has claimed multiple similar attacks. 

Iraq: Fallujah returnees complain about security and services

Source: Agencies