The extremist IS militants attacked Hashd Shaabi positions near the town of Khanaqin, some 165 km northeast of the capital Baghdad, Sadiq al-Husseini, head of the security committee of the provincial council, told Xinhua on Thursday.
There was no immediate report about IS militants who fled the scene after the arrival of reinforcements, al-Husseini added.
A joint force from the Iraqi army, police and Hashd Shaabi members started a search for the attackers, he noted.
Despite repeated military operations in Diyala, IS remnants were still hiding in rugged areas near the border with Iran, as well as the sprawling areas extending from the western part of Diyala to Himreen mountainous area in the northern part of the province.
The security situation in Iraq was dramatically improved after Iraqi security forces fully defeated the IS militants across the country late in 2017.
IS remnants, however, have since melted in urban areas or resorted to deserts and rugged areas as safe havens, carrying out hit-and-run attacks against security forces and civilians.