Clashes have broken out between Iraqi security forces and militants on the outskirts of Tikrit.
The clashes come a day after Iraqi and Kurdish troops backed by US airstrikes dislodged Islamic militants from a strategic dam in the country's north.
They began on the south-western outskirts of the militant-held city of Tikrit, located about 80 miles north of the capital, when a military convoy was travelling along the main highway that links Baghdad with the northern provinces.
The Iraqi military shelled militant positions inside and outside the city. There were no immediate reports of casualties.
Sunni extremists from Islamic State group have occupied Tikrit and the northern city of Mosul since early June, as well as large parts of the country's north and west. The militant onslaught has plunged Iraq into its worst crisis since the withdrawal of US troops in 2011.
The group has since imposed its own harsh interpretation of Islamic law in territory it controls in Iraq and neighbouring Syria.
Sporadic clashes have been reported around Tikrit and other areas since then, but efforts by Iraqi government forces and allied Sunni tribal militiamen have failed to push out the militants. Earlier this month, the tomb of former Iraqi dictator Saddam Hussein located near Tikrit was damaged in clashes between security forces and the radical group.
On Monday, Iraqi and Kurdish forces recaptured Iraq's Mosul Dam less than two weeks after it was seized by the militants. The dam is the largest in Iraq and a vital power and water resource for the country.
The gains made by the militants brought US forces back into the conflict for the first time since they withdrew in 2011. America's renewed involvement on the battlefield was a reflection of the growing international concern over the Sunni extremist group. Washington began carrying out dozens of airstrikes on August 8.
Hours after retaking the dam, US president Barack Obama called the development a "major step forward" in the battle against the group.
Obama said a breach of the dam could have had catastrophic consequences and endangered US Embassy personnel in Baghdad. He said the US was urgently providing arms and assistance to Iraqi security forces as well as Kurdish fighters fighting the extremists.
"We've got a national security interest in making sure our people are protected and in making sure that a savage group that seems willing to slaughter people for no rhyme or reason other than they have not kowtowed - that a group like that is contained, because ultimately it can pose a threat to us," Obama told reporters.