The Iraqi military says its forces have begun an operation to storm Fallujah, which is controlled by Islamic State (IS) militants.
The forces recaptured some areas in a southern suburb and took up positions on the eastern and northern fringes, leading to fierce battles.
Correspondents said explosions and gunfire could be heard on May 30 in Fallujah's southern Naimiya district.
Some 1,200 IS fighters and 50,000 civilians are believed to be inside Fallujah, a mainly Sunni city about 70 kilometers west of the capital, Baghdad.
As government forces advanced, a wave of bombings claimed by the IS group in and around Baghdad killed more than 20 people.
News of the assault comes a day after the Iraqi military said special forces had completed a troop buildup around Fallujah.
Iraqi forces, supported by Iranian-backed Shi’ite militia and backed by aerial strikes from the U.S.-led coalition, began the operation to recapture Fallujah on May 22.
An Iraqi military officer said on May 29 that troops had recaptured 80 percent of the territory around the city since the operation began.
WATCH: Iraqi forces have begun a direct assault to retake the western city of Fallujah from Islamic State militants. Reports said heavy fighting could be heard on May 30 in the southern part of the city. (Reuters)
In January 2014, Fallujah became the first Iraqi city to fall under the control of the militants, six months before they declared a caliphate over territory seized in Iraq and Syria.