The Iraqi army stormed into the southern edge of Falluja under U.S. air support Monday and captured a police station inside the city limits, launching a direct assault to retake one of the main strongholds of Islamic State group militants in the Arab countrty.
A Reuters TV crew about a mile (1.5 km) from the city's edge said explosions and gunfire were ripping through Naimiya, a district of Falluja on its southern outskirts.
An elite military unit, the Rapid Response Team, seized the district's police station at midday, state television reported.
The battle for Falluja looks to be one of the biggest ever fought against the Islamic State group. The city's pre-IS group population was around 320,000.
Falluja is the Islamic State group's closest bastion to Baghdad, and believed to be the base from which the group has plotted an escalating campaign of suicide bombings against Shiite civilians and government targets inside the capital.
The militias, who took the lead in assaults against the Islamic State group in other parts of Iraq last year, have pledged not to take part in the assault on the mainly Sunni Muslim city itself to avoid aggravating sectarian strife.
The Iraqi army launched its operation to recover Falluja a week ago, first by tightening a six-month-old siege around the city 50 km (30 miles) west of Baghdad.
A Shiite militia coalition known as Popular Mobilization, or Hashid Shaabi, was seeking to consolidate the siege by dislodging militants from Saqlawiya, a village just to the north of Falluja. Shiite fighters have been among the most effective in the battle against the Islamic State group, and the U.S. has altered between supporting and disavowing them due to their connection to Iran.
Falluja, in the heartland of Sunni Muslim tribes who resent the Shiite-led government in Baghdad, was the first Iraqi city to fall to Islamic State group in January 2014. Months later, the group declared its caliphate in Iraq and Syria.
On Monday, army units advanced to the city's southern entrance, "steadily advancing" under air cover from a U.S.-led coalition helping to fight against the militants, according to a military statement read out on state television.