Militants have ambushed a truck convoy carrying Shiites in a remote area in northern Iraq killing 14 people, police say.

The attackers first fired mortar rounds at a nearby military base and bombed a communication tower to draw security forces' attention away before intercepting the convoy.

All the casualties were Shiite truck drivers from Baghdad and their helpers. Their bodies were found with gunshots to the head. The attack happened near the city of Tuz Khormato about 200 kilometres north of Baghdad.

Attacks on civilians and government forces have escalated across Iraq recently. More than 3,000 people have been killed since April.