Security sources and residents said the attack on Samarra was launched at 5.30 am (local time) when two ISIS suicide bombers blew up their cars in the northern area of Sur Shnas.

At the same time a man drove a Humvee rigged with explosives into the south of the city and detonated it, while ISIS fighters attacked security forces to the west with sniper fire, mortars and rocket propelled grenades.

Thousands of troops and fighters from Shiite militias known as Hashid Shaabi (Popular Mobilization) have gathered around Samarra for a campaign to drive ISIS out of nearby strongholds on the Tigris River, including the city of Tikrit 50 km to the north.

In the town of Ishaaqi, about 20 km southeast of Samarra, snipers shot dead two Hashid Shaabi men as they tried to set up a sand barrier on the main highway linking Samarra to the capital Baghdad.