DEFENCE Minister Khaled al-Obeidi said today that he expects security forces battling against Islamic State (Isis) extremists to reach the centre of Tikrit within three to four days.

The operation to retake the city is “essential to opening a corridor for security forces to move from the south to Mosul,” he said, referring to Iraq’s second-largest city and the biggest Isis stronghold.

He described the operation as “100 per cent Iraqi, from the air and ground.”

Rockets and mortars echoed across Tikrit today after Iraqi security forces pressed ahead, having entered the city for the first time on Wednesday from the north and south.

Mr Obeidi forecast that the army troops and allied Shi’ite militiamen, Sunni tribes and paramilitary police, 30,000 men in all, would launch phase two of the offensive later in their bid to reach the city centre.

Isis militants are trying to repel security forces with snipers, suicide car bombs, heavy machine guns and mortars, he said.

Intercepted Isis walkie-talkie signals could be heard calling for reinforcements and ordering mortar fire on the soldiers as they closed in.

Along the route between Salahuddin’s command centre and the battlefield, the charred remains of tankers and cars used by suicide bombers litter the roads, while homes bear the signs of months of war, damaged by bombs and bullets.

Military officials say that they are advancing with caution in an effort to limit damage to the city’s infrastructure so that residents can return quickly once Tikrit is retaken.