According to al-Alam correspondent in Iraq, Security Forces (ISF) are now in control of the city's military hospital and a number of other government buildings close to the city centre.
The offensive is made up of tens of thousands of government soldiers and Shiia militias that have been pushing towards the ISIS stronghold of Mosul since last week.
Tikrit, the home city of former dictator Saddam, lies on the main highway between Baghdad and Mosul and will be the first Sunni city liberated from ISIS if it falls.
Yesterday, the ISF and militia fighters captured towns on the outskirts of Tikrit including Al-Alam, but made slow progress clearing the streets of mines and booby traps.
ISIS militants have planted an estimated 6,000 mines inside Tikrit, slowing down the joint operation to enter and retake the city," Ahmed Abdulla al-Jubouri, Iraq's provincial affairs minister said.
Last night the pro-government forces had advanced within yards of central buildings.
These included the city's provincial council and the office of its governor as well as surrounding the palaces of Saddam Hussein on the edge of town.