According to eyewitness reports the attack on Samarra was launched at 5.30 am local time when two Islamic State suicide bombers blew up their cars in the northern area of Sur Shnas.
In a parallel attack a man drove an explosives-packed Humvee into the south of the city and detonated it, while Islamic State fighters attacked security forces to the west with sniper fire, mortars and rocket propelled grenades.
In Samarra three Shiite militiamen were killed and six wounded in clashes as residents reported black smoke billowing over parts of the city, and hearing powerful explosions.
Thousands of troops and fighters from allied Shi'ite militias have gathered around Samarra for a major offensive to drive the Islamic State out of nearby strongholds on the Tigris River, including the city of Tikrit 50 km to the north.
