TIKRIT, Iraq >> Iraqi troops have launched the final phase of an offensive to recapture Saddam Hussein’s hometown of Tikrit, an official said Thursday, hours after the U.S. launched airstrikes on the Islamic State-held city.

Clashes intensified as Iraqi troops and special forces moved toward the city center, Lt. Gen. Abdul-Wahab al-Saadi told The Associated Press. Earlier Thursday, an Associated Press reporter heard a second round of airstrikes over Tikrit.

The Islamic State group seized the Sunni city last summer during its lightning advance across northern Iraq. The battle for Tikrit is seen as a key step toward eventually driving the Islamic State group from Iraq’s second largest city Mosul, which is further north.

In an address late Wednesday, Iraq’s Prime Minister Haider al-Abadi said Iraqi forces began the “final phase” in the Tikrit offensive but did not acknowledge that coalition forces were playing a direct role. He said Iraqis, “and not anyone but you,” will claim victory against the militant group.

At Iraq’s request, the U.S. began airstrikes on Tikrit on Wednesday in support of the stalled ground offensive, Lt. Gen. James L. Terry, the commander of the U.S.-led campaign to defeat the Islamic State group, said Wednesday.

He said the airstrikes would “destroy ISIL strongholds with precision, thereby saving innocent Iraqi lives while minimizing” unintended damage to civilian structures.

The U.S. first launched airstrikes to reinforce Iraq’s embattled military in August.

Iranian military advisers have been providing significant support since the Tikrit offensive began on March 2, arming and training Iraqi Shiite militias, which have played a prominent role on the battlefield. Militiamen make up more than two-thirds of the force fighting the Islamic State group in Tikrit.

Associated Press writers Vivian Salama in Baghdad and Robert Burns in Washington contributed to this report.