Islamic State suicide bombers and fighters struck targets yesterday in the northern Iraqi city of Samarra, where security forces and their Shi’ite militia allies have been gathering for an offensive against the radical Sunni militants.

Security sources and residents said the attack on Samarra was launched at 4.30am when two Islamic State 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 Islamic State fighters attacked security forces to the west with sniper fire, mortars and rocket-propelled grenades.

Medical sources said Samarra hospital received the bodies of 14 Shi’ite militia fighters and policemen.

Residents reported seeing black smoke over parts of the city and hearing powerful explosions. After heavy clashes in the morning, the fighting appeared to have subsided by the afternoon.

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

The army shelled northern and western districts of Tikrit yesterday, but did not send troops into the city, security sources said. Army helicopters had also fired rockets at Islamic State militants around Sur Shnas, they said.